LHR-DAY, via IAD or EWR with short connectiont times. Realistic?

I am looking to book an award reservation from LHR-DAY, an there are many connection options in either EWR or IAD, but most have only about a 1 hr. 30 min. connection time in either EWR or IAD. Is that enough time to connect to my DAY flight? Especially with Passport Control and Customs, transferring baggage from Customs, and in the case of EWR, having to likely go through Security again. At EWR, I would think that it might take an hour alone to get through Passport Control and Security. So, I was wondering with such short connection times, 1 hr. 30 min. are these realistic at either EWR or IAD to connect to my DAY flight?

There is one flight that departs LHR at about 4:20 PM to IAD, and gives a longer connecting time 2 hrs. 23 min., so I'd feel better about making my DAY flight, but it's a late evening flight getting me to DAY at 11:29 PM. I am somewhat okay with that, but would be nice to get in earlier, which makes them tempting to consider, but all such earlier flights have the 1 hr. 30 min. connection time in either EWR and IAD.

Any how, long story short, is such a short connection time really possible or realistic? After all, there seem to be quite a few flights offering such short connections, I can't help but wonder, are a lot of people missing their connecting fights, or does it really work out for them? Thanks.