Hi, @sliddy, and welcome to the forum! in the same position, I’d be tempted to get the IRS off my back and then start power-saving for retirement. If you’re saving in a 401(k) or other retirement plan with a match, then contributing at least enough to get that full match is a good idea, but otherwise I can’t see much advantage in dragging out the installment agreement if you don’t have to.
The FIRE movement (financial independence, retire early) is mostly younger people wanting to retire super early, but you might find some inspiration and advice that’s helpful in getting you to a comfortable retirement in a relatively short period of time. Plus, here’s a column that might be useful: