I would say that easement agreements are necessary to make sure you can even USE that section of road, let alone keep it maintained.  The current owners may have no problem with it, but if they ever sold the property you could have real problems if you don't have an easement in writing.  And yes, it should be filed in the Registry of Deeds.

I don't know if there is a specific form you can use; however, I can show you a few examples.  Go to this link:  https://i2a.uslandrecords.com/ME/Cumberland/D/Default.aspx

(I think that should work - let me know if it doesn't.)

Click on any one of the deeds at the left, then click on View Images on the right.  You can use the magnifying glass symbol at the top of the page to blow it up.  The three on this page were all by the same person, but each is a bit different.

If you know of anyone who has an easement deed, you can look theirs up in the appropriate county registry to see other examples.

Ah, that's different!  As long as you have easements to use the road, I don't believe you would have to have a separate easement in order to be allowed to maintain it.  The statute (23 MRS 3101) mentions obtaining an easement for ditches, in case it's necessary to encroach on private land in order to provide drainage, but it doesn't say anything about having to have a maintenance easement in order to provide maintenance for the road itself.  

What do the members' deeds say about the easement?  If it's an easement for ingress and egress, that would imply that it has to be kept passable, or it would cease to serve its function.  You might not be able to substantially increase what the road is, i.e. widening, paving, etc, but you should be able to provide whatever maintenance is necessary for it to serve as an ingress and egress.

I don't quite understand why a landowner would think a maintenance agreement would increase his taxes.  Can you explain?  A more common complaint I hear is that a town ought to decrease taxes if a person has to pay road association dues or otherwise contribute to the cost of keeping his own access passable.  A good part of our tax dollars go towards road maintenance, so it seems we ought to get a credit if we have to pay an additional fee to provide maintenance of a private road that the town does not maintain.

Ah, now I see what triggered your concern.  The "easement to allow winter plowing" does not apply to private roads that are privately plowed.  It sounds like the wording in your deeds covers that, as an easement to provide access will not provide access if it becomes impassable due to lack of maintenance or snow removal. 

Rather, the "easement to allow winter plowing" refers to public plowing of private roads under 23 MRS 3105-A, which says:

"The inhabitants of any town or village corporation at a legal town or village corporation meeting may authorize the municipal officers of the town or assessors of the village corporation to use its highway equipment on private ways within such town or village corporation whenever such municipal officers or assessors consider it advisable in the best interest of the town or village corporation for fire and police protection. "

The "private way" referred to in this section is defined in 23 MRS 3021 as being the same thing as a "public easement."  A number of years ago the Maine Courts decided that it's unconstitutional for a town to use its equipment to plow private roads, because that would be using public funds for a private purpose.  Many towns had been plowing private roads for years as a courtesy to their taxpayers.  But when the Court rendered this decision, it left residents on these roads in the lurch. 

Many towns have used section3105-A as a loophole.  If the residents on a private road can all agree to grant the road to the town as a "public easement," that makes plowing it a public purpose to keep the easement open for public use for fire and police protection.  But it still has to go to a vote of the townspeople to authorize the municipal officers to use town equipment for that purpose, and if the town has not already been plowing the road, that will raise taxes, so voters are likely to vote against it. 

Also, by designating it a "public easement," the owners open it up to unrestricted public motor vehicular use.  So while it may have solved the problem of how to continue plowing that had already been done for years, it's questionable whether it's worth trying on a private road that has always been privately plowed.  Once the public has free use of the road, it may result in further wear and tear on the road.  It's unlikely that the town will extend their authority under section 3105-A to doing summer maintenance as well as snow removal.  That leaves the members of the road association providing maintenance of what is now a public road, at private expense.   The Court has yet to rule that unconstitutional, although in my non-attorney opinion, that constitutes a taking of private property (maintenance dollars and materials) for public use without just compensation.  As long as the road is a dead end, this may not be much of a problem as there would be little reason for members of the public to use it.

The Town of Windham has been struggling with this issue, as over half its roads are private and the Town has plowed them for decades.  This year they got the Maine Legislature to pass "private and special legislation" that specifically grants the Town of Windham immunity for one year (with a possible one year extension).  That gives them time in which to get private roads to form road associations and then grant public easements to the town so they can legally continue their long practice of plowing these roads.