ExBoot provides two easy ways to manage this.
1) There is a something called a Synthetic Backup policy, which can be set to be manual or automatic. What it does is it automatically merges first then deletes the oldest incremental in sequence until there is enough space to do a new incremental backup.
2) You can set up Cyclic Full Backup, which essentially performs a full backup every X number of days specified. Each time a new full back is done, all previous incrementals are deleted because the new full backup is newer then all previous incrementals. Hence the older incrementals cannot be used anymore.