That of course is your decision to make but a wise decision is difficult to make because it depends on knowing the consequences of not getting the update immediately.
I usually peruse the description of the change (the changelog) and if it gives a CVE number, follow the link to the CVE description - to decide whether to reboot immediately or leave it until the next normal reboot.
If it says “allows unauthenticated remote attacker to do arbitrary code execution with privilege escalation, being actively exploited in the wild” then I would say “reboot immediately”.
Perhaps best to put your comment here: livePatch service? if that is what you have in mind.
Does it actually enforce a reboot or merely give the user hassle about choosing to reboot now or reboot later?
Ubuntu seems to a) know which updates even require a restart and b) give the user the choice of now or later.