An end to tinkering?

[ExtremeFiretop]

That's OK. It will be worth it in the end to ensure a stable setup. Will we be likely to get any notification that we'll need to do this (I'm thinking of users of MerlinAU like myself who may not be doing manual firmware checks) or should we just assume it will be necessary once MerlinAU notifies us that a new firmware has been detected?

MerlinAU will notify you of the available update like any other, it will flag some high risk phrases as well based on the current changelogs for 3006, and send an email about that.

Due to the VPN backend differences, it's strongly recommended
to do a factory default reset after coming from the original
Asus firmware if you used any VPN-related functionality.

MerlinAU itself won't advise that a reset is required, if you approved the changelog check it's expected you have read the fact that a factory reset is recommended after the update.
Keep in mind (so far) only users of VPN related-services seem will be expected to factory reset based on the changelogs for 3006