Exactly. 7-8am is peak checkin time (see the tsa website for averages).

IMO 45 min would be quite risky if you have baggage to check since the lines for checking and screening are variable and beyond your control (even curbside check has been known to back up).

If you checkin online and have no bags to check, you are probably okay with 45 min if the elite line is open (usually the case at 7am, but not always true in the evening and other times). If you can use the secret line near the walkway to the international terminal it may go even faster for you.

Personally I aim for a 1 hour margin no matter where I'm going to account for unexpected delays, i.e. traffic en route, car rental return, TSA mess, etc. It's just not worth it to miss your flight anymore, particularly at the end of the day when the planes are full and you might get stuck overnight. Maybe less risky in early a.m. if you don't have to be somewhere on time.