As long as the bottom of the wicks are in the oil they should be fine. As a kid I put olive oil into an old wick lantern and found it in the garage about 5 years later. Didn't think it would work but I struck a match and it lit right up. So I'm sure your paraffin oil lamps are fine. If you don't already use it, I'd recommend Ultra Pure Paraffin oil. Its only a buck or two more and burns a lot cleaner than regular paraffin oil.