6 years is not old but if you hire the problem fixed you may as well put the money towards a new unit. I agree it's low on freon or partialy blocked cap tube. With a 50/50 chance it's low on freon and leak is too small to locate with sniffer,if you have the tools and knowledge to work on it,I would think it worth installing an access valve and adding refrigerant. If you don't have a vacum pump and/or brazing torch available,cheap out with a self pericing saddle valve. If the problem proves to be low charge,go two steps farthur. Add a bit of flouresent under black light leak detector. When and if the detector pinpionts the leak,consider if it can be brazed up. If it can be brazed you should be able to have it done at a reasonable price. And for goodness sake,replace saddle valve with one brazed in while they are at it.