Linux noob question regarding full / partition

Background: I started daily driving Linux (specifically Mint) several months ago and for the most part it's been great. Some weird hiccups occasionally but nothing I can't handle/deal with. When doing my research to set the system up for the first time, I decided to go with 30GB for the / partition and ~220GB for the /home partition (the other half of the drive is for Windows 11 and the various essential tiny partitions). For a while this seemed to be fine, but lately I've been starting to get warnings when performing software updates via the Update Manager that the / partition is running out of space. I think it peaked at maybe 90-95% full a few weeks ago, at which point I started doing some research and cleaning up a bit (apt autoremove, deleting old logs and kernels, etc). I was able to claw back ~4GB and kick the can down the road, but now the warnings have returned and I'd like to handle this properly. I'm working from the assumption that I simply made the / partition too small and intend to double it by giving it some of the Windows space.

My question: How do I know if this is expected or if I've been doing something wrong? Is 30GB indeed too small on modern Mint, or should that have been enough? I know it partially depends on what all I actually do with the computer, but I really don't have very many applications installed (aside from defaults of course) and only four of them are Flatpaks, which I read tend to be larger. If it helps, the Disk Usage Analyzer reports that within /, /usr is taking up 13.2GB (55%), /var accounts for 9.1GB (38%), /opt is 1GB (4%), and everything else is <1% each.

Thanks in advance!