Assuming you're flying coach and don't have priority check-in, 90min is not a good advice if you're checking bags. 90min or even 80min will do most of the time, but sometimes it'll be too close for comfort. I advise 2hr if you want to be safe with near-certainty. I know there's been a thread on this.

At best, train platform to gate is 30min inc bag check. On average, I'd say ~50min. On a really busy day, it can take >75min total. If you're flying Y, you'd want to get to the gate within ~5min of boarding time. Train arriving 90min before departure time does not give much cushion for making the boarding time even on an average day. On a very busy day, you'll cut if real close even for departure. Note I'm saying this based on my recent experiences flying out of T1 on airlines without priority check-in (NH,SQ,AC,DL).

This past Jan, granted it was a peak travel day, but ANA bag drop was 40min wait. Then security was 15min. Interestingly, exit immigration was no line (usually it's a couple minutes at security, 5-10min immigration). I also had Internet issues and couldn't check in online. So check-in was probably another 15min. ANA refused to let anyone cut ahead during check-in. I arrived ~2hr before departure but only got to the gate pretty much right at boarding time.

I agree with Richmond being the best hotel in Narita city.