Is It Ok to Wait Longer Than 4 Weeks Between Ipl Sessions?

For laser hair removal, it is important to follow the time intervals that your provider recommends.  This will optimize your results.

It is important to follow the schedule that your laser provider has for your hair removal as the hair cycles and so its important to catch the growth phase of the hair at each cycle for optimal results. ~ Dr. Benjamin Barankin, Toronto Dermatology Centre.

On different areas of the body hair grows in at different rates.  I would advise you to keep to the schedule to have the best results.  Different areas of the body are advised at different intervals.  For example you can wait longer in between treatments for hair on the legs than facial hair.

From your statement I assume you are having your IPL treatments for hair reduction and not for discoloration and skin rejuvenation? Hair grows in certain cycles, so waiting more time won't help you get better results. The hairs will only be able to be treated if they are active, and if they are responsive. Waiting longer, in this sense, won't make them respond to treatment better. For hair removal specifically it's important to follow the time intervals given.