This is the important question, I think. There's nothing to worry about if the DS3025 is marked complete.
As far as AOS - there is no deadline to file AOS, as far as USCIS is concerned. (Not even an arbitrary 2 year deadline that has been mentioned here - that deadline doesn't exist). However, waiting to file past 90 days is a risk because at that point, the immigrant has no legal status in this country as @yuna628 stated. Once AOS is filed and the I-485 receipt is obtained, the immigrant has proof that they are authorized to stay in the US while their AOS is pending.
@Scandi summed it up perfectly in this post, from the thread where a VJ member was unfortunately detained for weeks because they were just a couple weeks late in filing AOS: https://www.visajourney.com/forums/topic/706560-beware-bad-information-on-aos-deadline-for-k1-fresh-out-of-jail/?do=findComment&comment=9705397