Ninety times with breaks

Dear Rabbi! I just read on your website that if one says the words “give dew and rain” ninety times, then, if one is in doubt whether he said these words during prayer, he doesn’t have to go back and repeat the prayer again. So, my question is this. Does one have to say these words ninety times in a row, or is it possible to break this into a few sessions, to say a few times today, and then a few more times tomorrow? For example, today I only managed say the words twenty times. Then I ran out of time. Can I say it thirty more times tomorrow, and then a few more times the day after, until this will add up to 90 times?

Dear …

Saying these words 90 times not in one sitting also helps one get used to saying them. Therefore, you can definitely divide this into several sessions, and even into several days.

Shulchan Oruch, section Orach Chaim, ch. 114, §9