Officially poly only 6 months (never knew the word before that anyway).
But I've been with GG to some degree or another since I took his virginity something like 15 years ago and with Maca for 12 of those years........
I see NO end in sight. I see both of these relationships lasting til death.
So no-I don't think that's too much to ask.
BUT making it last requires a willingness on ALL parties sides to put for the effort in ALL relationships. Most people these days aren't willing to do that in ONE relationship (i.e. the high rate of divorce), so there aren't going to be a LOT of us who manage that in more than one relationship.
Ask me in another 20 years, I'll let you know if we're still together.