FYI, like the OP, i live in California, have a smaller 50 year old home, i have a 100amp box, i have most of my breakers split, i have a reef tank, i have a refrigerator, i have a microwave, i have a GAS stove, i have a dishwasher and a garbage disposer, i have dedicated kitchen receptacles, i have a washer AND a GAS dryer, my PC is always on, i have a crazy home theatre system, recessed lights, i have all of those things and never once have i tripped the main. Granted, i don't have an A/C because i don't need one but i have alot of things plugged into the wall. If you look at my tank specs below in my signature you'll see what i run. With most of todays appliances being energy efficient, i just can't imagine it happening. 100 amps is alot. Even 80 amps is alot for a home my size. I'm just saying that it can be done. I've been doing it this way for several years.
We don't even know anything about his living conditions. Is it a small 2BR house? Does he live alone or with a family of 10? All of these things factor into his decision on whether or not to upgrade the panel. It isn't cheap and with the prices of contractors here in California, it is much more expensive than probably 99% of the rest of the united states to have such work done. Sure, its easy to sit behind a computer and tell the guy "just upgrade your panel........" but when it comes down to it, these factors all have to be considered. I also got a couple quotes to upgrade my panel and it was around 3.5k. I was able to put it off because i knew i didn't need it. It would be nice....but we didn't need it. We have a small house, a small family and updated appliances. I'm not saying that everyone is wrong in telling him that he needs to upgrade, but IMO what i am saying is that depending on his lifestyle, he may not even be close to exceeding those limits.