If the property taxes are reasonable in Maine, that seems like it may be a great retirement location for you... in determining where we want to live over the long haul, taxation is a big factor, in my opinion. I'm guessing that the taxes on your property in Boston are very high... perhaps prohibitively so once you are retired, even if you have no mortgage on the property. So, if you are planning to eventually move there, perhaps you would think about it differently.
Do you think you would want to purchase an existing home with the plan of eventually living in it after you retire? If so, maybe you would want to rent it out until you are ready to retire? Are you close enough to manage the property and keep maintenance on it (and making sure your renters are taking care of the place)?
If you buy unimproved land, you could certainly build a home there later on, after you retire, perhaps? Unimproved land doesn't have the worry that a vacant home would have as far as vandalism/squatters, so maybe that would be a good idea since you aren't really that close to retirement?