If you are shoooting smokeless, you might look inside a few times a year, but you should have removed the sideplates when new to check it and lubricate the links etc. I use white Lithium grease on the links and pivots.
You didn't mention the caliber. If it is a 45 or 38 straight case, then check the extractor for blowback debris under it, if there is blowback stain on your brass. Crud built up under the extractor will lift it over time and eventually give extraction problems.
A 44-40 has much less blowback into the action, and is best for that reason if you are using black powder loads.