Congratulations on your first 600 series! I still recall mine too, and I can go back to my sanctioned 600+ Series Logbook and I can tell you the series, date, game scores, pair of lanes, house, and the league that I bowled it on, and I'm talking over a decade ago! Now's your chance to start your own 600+ Series Logbook too, since you have your first entry already. Also, congrats on a fine 258 game!
That first sanctioned 600 is a milestone indeed. Now, the next barrier is the 700 barrier. But, in the meanwhile, keep up with all of your sanctioned 600's too....it can make for a good souvenir, and it can give you an idea of your progression of your game.
As for setting a high average, don't sweat it. This should give you the momentum to see just how high you can keep the average up during the summer league. Also, if you have a winter league average on the books, the higher summer average won't hurt you come tournament time, since most tournaments want winter league averages.
I too did something like you did a few years back on a summer league. On the first night of the league, I shot 244, 226, 299 > 769, setting a 256 average! Of course, my average came back down to earth before the end of the summer league.....I'm not even a 220 averager, so it didn't take long to bring down the 256 average. Don't sweat the average.
