Back a few years ago 3 hours was a medium ride. I remember I once did the morning race ride at 6:30, then rode to half Moon Bay and back just in time to meet up with the noon ride and do that. That was during an unemployed period lol!
More typically I'd do 2 to 2.5 hours during the week and 3+ Saturday and Sunday. Often the 3+ was a road race or 2 crits+warm up and cool down.
Currently I finally got back to where I can do the longer rides and trying to get one in most weeks. I wake up late and for me a long ride is an all or most of the day activity. I don't think I'd really get more benefit from doing a few per week other than the total mileage benefit. At some point if you wanna get more time on the bike more of the rides end up more than 3 hours, considering 2 rest days per week.