These questions should help you figure out whether you have a kidult playing PlayStation on your couch:
#1. Are his toys age appropriate?
An hour-long football sesh with the boys on a Sunday is one thing. Three hours building expensive train tracks in another room when your colleagues are over for dinner is another!
#2. Can he pay his bills?
...or at least take responsibility for his finances and save for his future?
#3. Does he prioritise his friends above all?
Pay attention to the pedestal he puts his friends on. Does he do whatever they want him to, with no healthy boundaries in place?
#4. Does he chuck the dummy?
Find out whether your man deals with confrontation in a mature way, offering solutions and reasonable arguments instead of getting irrationally sulky when confronted.