I have some NiCd packs that are over 10 years old and still in use. They cycle to near capacity and have good self-discharge rates. I have also had NiCd packs that lose significant capacity after only 3 years.
The 500 - 600 mAh AA packs that come with Futaba and Tower FM radios seem to always last many years. I suspect they are made from Sanyo's high-reliability cells. Higher capacity packs seem to have a shorter lifetime. All my 1100 mAh AA packs have lost capacity after 3 or 4 years.
You should test your pack for capacity and self-discharge rate. If you don't have the equipment or don't want to do this then I recommend that you just get a new pack. Using an old pack without testing if would be too risky.
There was an excellent web site written by a professional battery engineer that discussed NiCd lifetime. It was www.rcbatteryclinic.com
. I think the website has been taken down. Maybe you can find it with a google search.