here's another view. These are huge!

a close up of a flower with some damage/bugs ? on the leaves.

Ok, I've read quite a bit and have a couple of thoughts. Is cutting 1/3 of the plant the right approach rather than a full rejuvenation cut down to 2-3 feet of bark? I don't think 1/3 will be enough though. There are a lot of trunks per plant and the plants are roughly 10 feet high by 8 feet wide...but the width is uneven, meaning they have grown for decades from the base to one side, probably due to the hill and sun. Several trees were recently cut down in our neighbors yard, so these Rhodos will get more sun on (what is now) the short side. The blooms have just started to fall off and the plants will start growing now, based on what I've read. So, cut 1/3 (or 1/2?) now after the bloom or wait until the end of winter and rejuvenate cut severely. are these my choices? any thoughts would be great! thanks

one more photo

Where I live, what you propose is a pretty common practice. When our tall growing native rhodies get too gangly or other, hybrid rhodies get leggy because of too much shade, it is not at all unusual to cut them back hard, sometimes to nearly ground level stumps. Almost without exception they will resprout from this point with some nice new, dense, lush growth. However, it can take some time before this new growth materializes or begins too look very attractive so patience is important :-))

And in my climate, this somewhat radical practice can be done just about anytime of the year, although I'm not sure I'd recommend that same casual attitude everywhere. Early spring as the shrub is pushing new growth anyway would be ideal but you can probably get away with it now as well. Just don't wait much longer into the season if you choose this option.

I would think it's already too late in New York Z6. You do not want to go into the winter with a lot of soft new growth stimulated by pruning. This is likely, however, to be rhododendron maximum or a hybrid of that species if it has just finished blooming and is only now starting to put out this year's vegetative growth. In that case, cutting back now may be fine or at least no different than what happens naturally.

As for the rest, the practice of decreasing the size of large old plants by doing a third at a time is a common recommendation and has the virtue of preserving a good portion of the plant if the first cut back fails to break new buds. From the last photo, much of the direct sunlight seems to be coming from the house side of the deck. If no sunlight will actually reach the the cut back portion of the rhododendron, the chances of vigorous new growth from the remaining stems may be diminished - this is true of some rhododendrons but not all. If there is a place where the pruned branches will receive sun, that's probably the best place to start.

In an eastern Z6 climate, be prepared to exercise considerable patience. It will take much longer for the plant to regrow and recommence blooming than it would in a more benign climate such as the PNW.

The pruned branches would receive sun, so now I will wait until the very early spring of next year and cut it back severely. I have patience, so waiting is no problem. Thanks for the advice, you helped me make my decision!