So in case of timely notifications it's a pain. The notifications are delayed on purpose by Android to save the battery - by not waking up the phone when an app wants it, but when Android decides it's time to wake up...
You can try to remedy that going to Android Settings > Apps & notifications > See all apps > Goalist > Advanced > Battery > Battery optimization > switch to "All apps" > Goalist > Don't optimize.
Will it drain your battery? It depends on your battery and how much you use:
* Goalist in general
* Reminders
* Periodeus
* Goal Monitors
* Nagger
We use a lot of all these with a high frequency Nagger and even if it meant higher battery usage - we care more about having timely notifications than full battery.
In our opinion it's much better to have only important elements enabled and attend them, than having 100 Goal Monitors, for instance, and look at them occasionally, if at all. So the optimization is in a curated list of Notifications, not in letting Android suppress / delay them.