Yes that is fairly normal.

The NiCd is an interresting beast. It has an S-curve voltage characteristic. Early n discharge the voltage drops VERY fast, then it levels out for most of the useable charge, then it starts to drop faster and faster. ( a VERY lazy S)

Peak is normally close to 11.0 for an 8-cell pack. You are right in there. The drop of 0.3 v over a few days is normal... the voltage will be about 10.5 to 10.6 at 1 week. The radio will function fine until the pack reads at 9.4, then things can start to go wrong. 9.6 is normally considered minimum to fly. (the rated voltage of the battery pack!)

Going below 9.4 and still flying is VERY dangerous. the voltage drop from there can hit flatline (no useful power) in just a couple of minutes.

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The reciever pack will have the same type voltage curve... just ranging from 5.6v (I've seen 6.0 once...on an overcharged pack straight off a quickcharger. That was one HOT battery[X(]) down to 4.6 as the absolute minimum you want to see. Again.. the label rated 4.8 v is considered time to recharge.

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A Nicd has 2 major enemies... lack of use, and heat.

If you don't periodically discharge and recharge (flying counts ) the battery can go bad in about 3 to 6 months. (sometimes they will be OK at 1 year... but that is rare.)

Anything that heats a NiCd above 120 deg F is a problem. A hot NiCd tends to outgass... which will create crystals on the outside of the cells. These crystals are corrosive and toxic. The crystals will desroy your batterie's wire lead, and can destroy the switch harnes (and occasionally the reciever.) Overcharging heats a NiCd quickly.

Overheated Nicds can explode. If you see any sign of bulging of a cell on a fast charger... get clear as fast as possible... its going to pop. You MIGHT save it from exploding by unplugging it... but you would be risking being in the area where fragments and acid will be spewed out. Let it pop. (then you have a hazardous material cleanup issue.... best left to the local fire dept.)