OK, hereby a follow-up:
karlchen and I have spoken about this in PM's, and he's trying to contact the Mint developers about this.
In the meantime you can use this workaround, when you want to increase the update interval:
https://sites.google.com/site/easylinux ... ew-updates
(item 1.2.2, left column)
That should ensure that you'll never miss update notifications, even when you've configured large intervals.
Thanks Pjotr for this workaround.
If I understand what it is doing properly, it is updating the local cache during initial bootup, rather than getting mintupdate itself to query the databases. It therefore relies on this happening before mintupdate checks the local cache at the time of initial login. I found that if I logged in too quickly, the local cache had not been updated, and the mintupdate query still returned no updates, until the next reboot. This could lead to the situation where the machine is only really presented with updates on every second boot.
I found that setting the timing to 30 rather than 50 made it more likely that mintupdate would have the new updates available for me each boot. Is there likely to be any problems in setting the timing to occur this soon during bootup?
Is there any command that can be used to run the refresh of mintupdate itself after login? My preference would be for the updates check to occur a few minutes after login, after everything has settled down. My vague understanding of other posts about this topic is that it is not possible to get mintupdate to refresh with a terminal command. However, your workaround is not exactly the same as a manual terminal command (e.g.; not requiring sudo)
Frankus333: LM18.3 KDE 64 bit; HP 15 laptop, 4GB RAM, CPU Celeron dual core N2840 2.5GHz, 500GB HDD (triple boot LM19.2 XFCE, Win 8.1)