I think for many, if not most, experienced poly people age becomes yet one other smaller factor in overall attraction to people. The more experience you get in Poly the less likely you are to say "here's the relationship dynamic I want, who fits it?" and you're more likely to say "I met this person and they're interesting and I'm attracted to them, let's see if we can make this work".
So really, it depends on if you find yourself compatible with an older couple or group.
Me: 30ish bi Female S: mid 20s bi MtF transsexual (presurgery)
Our Kids: D 8 yrs, boy (Mine only from prior relationship); T 2 yrs, boy; A under 1, boy
Living and Developing a relationship with L: 30ish bi Female and her husband B: mid 20s bi Male
Their Kids: Little L 3 yrs, boy, R nearly 2yrs, girl, Due November 2012
Favorite Poly thought (if you recognize help me find the source): Jealousy is not a disease, it is a symptom. To "cure" it you must identify the disease.