how often is PC used? You could use a program to track temps and then you can see over time how the temps increase. Helps to know what normal is after a clean so you have a baseline. Also depends if you have A/C or not.
I swapped AIO in December and have to wait a year to work out "normal" as I don't have A/C and temp in room depends on ambient outside. Winter now so temps are between 20 and 30c on my CPU, but I know it won't be down there in summer.
Knowing what range temps are in a clean state can help work out if you need a clean.
This is my unrealistic baseline for Winter, I doubt I get much lower this year:
first temp is CPU cores, then CPU package (exterior of CPU), then Nvme, then GPU (yes, screen is dirty, or was).
This is what I use to track my temps
Download HWINFO - https://www.hwinfo.com/download/ when you open the app, click the tick box next to show sensors only, and click run in the next window, click on the gear icon in bottom right, this opens settings. On General tab, under polling period, set it to 500 and click the set button...
forums.pcgamer.com
I like to know what my PC is doing since 90% of the time its just sitting idle and I notice if it suddenly starts doing something randomly.
Fan noise also increases as dust on fan blades makes them louder. That is actually how I figure it out first.