If you haven’t had any firmware update since you’ve had your Oticon hearing aids (are they OPN?), you may want to go back to your HCP to have them updated. My 2016 OPN 1 used to reboot fairly often in the beginning but after a few firmware updates, the reboot frequency has definitely decrease. However, it still does it once in a while, which is not too much to worry.
If you already have the latest firmware update and it’s still rebooting more and more often, it may be a sign of aging. If you are nearing the 3 year warranty mark, I would definitely recommend you take them back to your HCP and get them replaced for a brand new pair before your warranty expires. That’s what I did on mine, even if they don’t have obvious failure. Intermittent but regular reboots like your HAs definitely qualifies for warranty replacements.
Even if your hearing aids reboot less after the latest firmware update, I would still recommend you get them replaced for brand new ones under warranty about a month before the warranty expires anyway. More frequent reboots indicate signs that the hearing aids may be aging more and more anyway.
It’s only a guess, but if you have the same firmware all this time and your listening environment hasn’t changed but the hearing aids reboots more and more often, it’s possible that the internal memories are going bad more and more due to aging, and the bad memories may get blocked out automatically as they go bad, and with less built-in memory to work with, the buffers may get full sooner/prematurely before they have a chance to get flushed, leading to more frequent overflows and resulting in more frequent reboots to clear out the overflowed buffers.