While he never became a true combat asset, he did survive with me through many of my quests,travels, and undead infested caves because I simply was not interested in actually going that far to the East when I picked it up. Okay im not saying he survived outright I typically had to reload previous autosaves to keep him alive, but I was always able to finish the battles after a few tries. Sometimes I had to hit him so he would focus on aggroing me insteasd of the enemy so I could keep him close and heal him from time to time. Dragons seem to really like taking him out in the most pitiful of ways. Something I guess I have in common with them.
Eventually we got there and though I had resolved to finally kill him once I'd fulfilled my promise and got him to Eldergleam(I was convinced his goal was to asassinate me until I first checked out this wiki)...after a few attempts to get both the sap and the sapling(impossible) I had a change of heart and decided to let him live (though I stand by my mission to save Gildergreen not bring back some little sapling welp) so he can start a new (Dragonborne influenced) nature cult with the purposefully attractive devotee that lives there. I managed his survival by letting him speak his idea (eventually after belting him for insulting Whiterun and Gildergleam) but before I actually get the sap, I aggro him and let him chase me near the entrance to the main chamber of the sanctuary well away from the forthcoming spriggin battle and then you can either sheath your weapons so he'll "let you live" or sometimes he'll submit after a nice beating (this is unpredictable since he may flee from you right back into the forthcoming battlezone and he'll no longer follow you at this point unless you aggro him again. He shouldn't automatically aggro you after the spriggin battle he'll just be standing around where you left him in a daze marveling at the fact that he made it to the sanctuary.
Getting down from Eldergeam after tapping the sap fast enough to save the sanctuary devotees (they fight on "your" side against the spirggins but they both die very easily) is trickier and I recommend just jumping down to the path from the side of the Eldergleam tree after you take its sap to avoid the time consuming battles with the spriggin behind you and on the path..then I found it best to summon an antronoch to protect the gal (as well as having already posted my follower in that area to wait for me while I went to the tree) while I and my follower go toe to toe with the Mother spriggin thingy..I had trouble saving both devotees and... well... the guy dying kinda removes him from the equation as far as Maurice and the gal are concerned so its convenient for my RP that he dies(honorably in battle) anyway.
I chose to save Gildergreen because I gave my word and I don't see the nobility of letting it die when I know how to save it just by scratching up Eldergleam's evergreen size ego a little bit. Not instead bringing some feeble little sapling welp to take its place. I clocked Maurice for insulting Whiterun and Gildergreen...effing turncoat. After saving his life so many times I guess he forgot I was a Thane of Whiterun and pledged to save Gildergleam by any means. Besides, I figure if Maurice lives theres always the chance he'll take it upon himself to follow through on his bright idea and bring little saplings to Whiterun and Skyrim in general if hes so keen on spreading the beauty of Kynorat or whatever.