Apple Magic mouse often loses connection
Solution 1:
The thing is, you can fix your mouse with just your fingers. Simply remove the back cover and bend it so that ends curve up on the Apple logo side. Then, replace the cover. This is why buying a new mouse can fix the issue: Over time, the back cover starts to bend so that there is more room between it and the batteries.
Solution 2:
More people have this annoyance. For me the solution was to use slightly fatter/bigger batteries (Duracell for example), or a piece of paper. When I very gently slammed my mouse on the table from a small height, the connection would drop. Probably due to a short disconnection/movement of the batteries.
Solution 3:
The paper shim trick didn't work for me - it made the cover bulge enough to rub on the table top. The cover bending suggestion sound risky. So I combined the two as follows: Start with an 8 cm square of paper. Fold it in half three times, giving a 4 cm by 2 cm pad with 8 thicknesses of paper. Remove the cover and position it on top of the paper pad, centered, so it overhangs the pad by 2 cm on each end. Push down on the two ends until they touch the table. Replace the cover (without any paper shim) and test. If necessary, repeat with a pad that has 10 or 12 layers of paper.