I usually turn in the first one or two parts, but I always end up using them for poisons (with mod added ingredients). Plus I use a mod that makes them regrow. If I happen to be in Skingrad and have enough to turn in a segment, then sure.
And while the Elixir of Exploration may be better than vanilla with OOO (I run FCOM), they're still pretty craptacular.
On the other hand, Sinderion is a pretty good source for rarer ingredients, especially the toxic kind, so he's not a waste of space or anything.
Sinderion is almost my primary source for money. His exteremly high dispostion combined with his extremely low mercantile skill makes him the best trader for any alchemist. Just buy some apples and bread loves, spam fatigue potions and sell them to Sinderion.