If it a big thick RIS, In theory it could be aged for years in the secondary. Any beer over 1.050 will age well. I leave my RIS in secondary for at least 6 months, some times longer.
I have a few right now that have been sitting a long time. Didn't get them bottled before starting my addition/remodel and now to late to bottle without extra hassle. I hope to get my keezer up and running and carb them that way and see how they taste before getting rid of them.