Is there a age limit?
There is no age consideration for self-petitioning. We generally let you decide on whether you should apply or not. In general we have found that if a phd collects all the publications, awards, various efforts along his phd and during his work experience, they may collectively be sufficient evidence for a NIW (most cases) or EB1A (significant number of cases) self-petition. We suggest you look at the USCIS criteria and some example petitions.
Usually i-140 approvals are quick (generally few months and sometimes a year). Processing time I-485 depends on your country of origin and applied category (EB1 or EB2). If the priority dates are current it can be a few months. Please looks at the current visa bulletin to see the visa number availability.
Best of luck
Green card for Phd Team
Helping NIW and EB1A applications
with our DIY packages