Have you looked beneath the mouse for any debris stuck to the plastic grease ?(give your mouse mat a wipe too)
Also if you have a ball take that out and give it a clean ,Lay a strip of sellotape and roll the ball on it (you'd be surprised what sticks

)
finally get a cotton bud wet it and wipe the rollers in the mouse housing Guarantee you'll get some hair /fluff tangled casing thre rollers to slip hence the "jerks" are seen on the screen! with the pointer

Do this job every other week to keep it running a top performance

Take you 2 mins
I agree with you the Microsoft Mouse eats batteries

.Buy a pack from the cheap "everything for a $1" store or whatever they call it in your area? to keep you going
I too am using a cordless mouse but it is an A4Tech model IRW-5 Battery consumption is very good only change every 3 weeks

and This computer is used perhaps at least 4 hours per day? With occasional useage possibly squeeze 3 months or more out of the batteries

BTW This model is out of production, but here is the identical IRW-25 model which is colored 2-tone as to mine which is off-white.
www.a4tech.com/en/product2.asp?CID=1&SCID=7&MNO=IRW-25I found that the retail price is $25-$30 US

But I found a company with some at $12.99 US
Ergoshops Online Storein California .There might also be some on Ebay? so check that out?