I bowled in scratch leagues for about 3 years. I was a 210 avg bowler (or at least got up to about that high - was generally 200-205) and have bowled 290 twice (my high game), picked up 7-10 split once but no 300. Also, an 800 series ("series" in bowling = 3 games) is the other milestone that people go for and is a lot harder than a 300 game, and I've mustered 793 but not an 800

.
I will say that given 290 is bowling a spare then 11 strikes and after one of those 290s I started the next game off with 5 strikes, I HAVE bowled 16 strikes in a row across 2 games, but couldn't run a streak like that in 1 game. I have no idea how many 279s I've bowled...probably 15 or so. 279s are the devil. In probably half of those, the missed strike came somewhere in frame 3-5 and based on how I was bowling, I knew the score would end up a 279 because I knew I wouldn't miss again.
Our leagues had some damn good bowlers...I know at least one finished a league at over 240 avg before, one has bowled an 889 series and I've seen a few 1100+ 4-game series', have seen 2 300s in a series at least a few times, a bunch of 7-10 pickups, etc. Fun stuff.