Does the spacebar take more power?

[confus-ed]

Infrared? Might as well get wired instead of IR, I find IR much more trouble than wires.

Radio dude, I'll agree IR is a PITA, all that line of sight stuff wireless keyboard & optical mouse combi - best money I ever spent on my own pc

As for what to do with rechargeable batteries ..

Try this (pdf)

..Break In New Batteries
New batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge the new battery two to four times to allow it to reach its maximum rated capacity.

Prevent the Memory Effect
Keep the battery healthy by fully charging and then fully discharging it periodically. Exceptions to the rule are Li-Ion batteries, which do not suffer from the memory effect...

Memory Effect
NiCad batteries, and to a lesser extent NiMH batteries, are prone to what is referred to as the "memory effect". What this means is that if a battery is repeatedly only partially discharged before recharging, the battery "forgets" that it has the capacity to further discharge all the way down. To illustrate: If you, on a regular basis, fully charge your battery and then use only 50% of its capacity before the next recharge, eventually the battery will become unaware of its extra 50% capacity which has remained unused. The battery will remain functional, but only at 50% of its original capacity. The way to avoid the "memory effect" is to fully cycle (fully charge and then fully discharge) the battery at least once every two to three months. Simply leaving the device in the ON position and letting it run can discharge batteries completely. This will help insure your battery remains healthy. Once discharged, recharge the battery completely according to the manufacturer's instructions...

Exercise the Battery
Do not leave the battery dormant for long periods of time. We recommend using the battery at least once every two to three weeks. If a battery has not been used for a long period of time, perform the new battery break in procedure described above...