I hear that if you do not remove the seed pods the bush will not bloom next year. Is this so?
Should I Cut Off Seeds From My Lilac
Certified GKH Gardening Expert
While it will still bloom, leaving them could inhibit flowering (slow it down), so most people prune the shrub just after blooming. This article will help with that: https://www.gardeningknowhow.com/ornamental/shrubs/lilac/pruning-lilac-bushes-when-to-trim-lilac-bushes.htm