Cataracts surgery can be done whenever they start affecting your life. Previously you had to wait until you were almost blind,this is not the case anymore.
Depending on the cause, cataracts may progress in different rates, but they usually develop slowly.
I got mine very quickly - my vision went from perfect to half blind in a span of few months, but I'm told this is quite rare. I had the surgery on one eye already and I'm about to have another one In 2 weeks.
Surgery is quite straightforward, takes 10-30 minutes tops, most people have only local anesthetic, so you go home the same day.
I'd say, as long as they don't affect your everyday life, no need to worry. But once they start to be annoying, it may be worth to push for the op.
I had 20/20 vision all my life, with cataracts I went to only being able to read the top/second top row on the letters chart (at the doc's office). After the surgery, it's not back to perfect, but it's sooooo much better.
Apparently some cataracts can actually disappear, but I don't know how true that it.