I honestly didnt take many alts higher than 10-20 before deleting them and replacing them with another random idea.
If that's how it was fun for you, it's all good! As a chronic altitis patient, I can say it had its ups and downs. It was a heck of a lot of fun having an entire stable of characters that you could pick and choose from. Over time I could imagine them all interacting with each other, forming bonds or rivalries, having friendly competitions... and not-so-friendly competitions. Accidentally launching a rocket into the wall of the SG base when they took one of the Flyers out for a joyride...
On the other hand, in three and a half years of playing (most of it very casual in both time and effort, admittedly) I still only got one character to 50. A second came close, 48 and about a half. Two made it to 30-something... and the rest never made it past 22. I always meant to, but as it happens I had more fun making costumes for the Hero Dawn contests, talking to friends, badge hunting,
planning builds, and checking out the scenery than I actually did running missions. Go figure.
Altitis... when you love it, you love it, but it's not for everybody.