The way SFA is running I don't think half the rides will make it till then even...
Stealth's repeated downtime is very different.
It had its issue at the start of the season, which was a big unexpected hiccup from winter maintenance. Since then, it's had two, pre-planned, periods of downtime. One of them was for a launch cable replacement, which happens yearly. The other I do not know, but since it was short, pre-planned and stayed on schedule, I don't think is a major concern.
Rita has suffered longer, not-planned closures, with no known opening date advertised during those closures. That indicates that those issues are actual problems with the ride which needed fixing / parts replacing.
I don't think the two are linked, and it's more coincidence that there's two rides of the same time that have experienced downtime in the same year.