Re: Definitely pick which battles you want to fight...
Mice, keyboards, headphones, cables - all consumables.
printers, inexpensive laptops, small UPS devices, phones, and slabs, too.
Only a BEAN COUNTER would want to bother with DEPRECIATION SCHEDULES for anything valued less than $5k, unless it's an integral part to a system with a high enough value to justify it. I have _NEVER_ seen an advantage to doing depreciation for otherwise expensable equipment. It's like they're just making up work for themselves.
Now a rack of servers, UPSs, multi-port ethernet, and routers might be justifiable, but NOT EVERY! STINKING! CPU! BOX! AND! MONITOR!!! The purchase value isn't worth the cost of tracking them and the equipment rapidly loses its actual value over time like a new car off the lot.
Better (and easier, and probably cheaper) just to keep receipts and expense them all in the year they were purchased. You'd do the same for pens, toner, and any office supply thing purchased in bulk. And. any auditor can walk around the office and see that people are using the stuff and it would be an insurmountable task (and maybe even impossible) to verify every serial number against the visible number of company issued phones, slabs, laptops, CPU boxes, monitors, etc. in addition to the keyboards, mice, cables, headphones, and occasional entertainment devices.
Another thing: the phones and slabs are also likely to have SIMM cards in them issued by the company, which probably COST MORE IN A YEAR than the stupid phone or slab did. It would be POINTLESS to track the actual device they're inserted in. Many people would want a new i-device every year anyway. So you might as well just 'expense' them.
Seriously, I bet if you FIRED THE BEAN COUNTERS who are compelled to track things and justify their DEPRECIATION SCHEDULES through labor-expensive inventory audits, you could purchase NEW GEAR for EVERYONE every 3 years and not even WORRY about what happened to the OLD stuff, and STILL come out ahead financially.
[I think I'm starting to sound like Simon the BOFH]