Let the cell sit for a day or two without being in charger.
Measure voltage. Write the measured voltage down on a piece of paper and don't lose it.
If between about 3.5V to 3.6V, this is the optimal storage voltage, but even up to 3.8V is a fairly good storage voltage. Put it on the shelf, forget about it and go enjoy life.
Measure again after a year, maybe two. If it has significantly dropped from what you wrote down on paper, for example from 3.65V to 3.50V, the cell wasn't in very good condition to begin with, but it may be still usable.
If it has dropped below about 3.0V, the cell is dead, forget about it and dispose of it properly. Storage revealed this, but it was not the storage which "harmed" it, it was originally bad because it won't hold the charge properly. Proper cells survive storage at any state-of-charge without dying.
Actually storing for a long time is a surprisingly good "defect test" for mere mortals without expensive analyzer tools. A proper cell doesn't significantly lose voltage when kept below about 3.7V. To your question, after how many months you need to recharge - you don't! Well maybe you can check the situation after two years, but if the cells are any good, you likely won't need to recharge at all even after 5-10 years!
Finally, we know nothing about the quality of your cells. They might be bad counterfeits.