My summer home is on a lake in northern Michigan. We have hot summers and cold and deep snow in the winter, this is very hard on my deck. I have used a number of products to stain/seal the deck but the older is gets the harder it is to keep a nice look to the wood.
I am considering paint or a solid color stain. My question is what gives the best result and last longer? This every other year stuff is killing me.

Macstu

I would go with the stain . I think it lasts longer also when it is time to re up there is a lot less prep work

I agree with gleighvah, stain will work best with a sealer of coarse.
If you deck is 18 years old your done really well by the way.
You best investment if you can aford it will be to use a composite decking and handrails. Just think you'll never have to stain or paint again, and also in another 18 years it will look like the day you installed it.

Thompson makes a water proofer plus wood protector that comes in clear or tinted versions. I spray this on my decks and log side walls with a Wagner Paint Crew sprayer. It is difficult to go beyond 2 year intervals on horizontal surfaces even with a great product.

Never put paint on a deck unless your willing to oil prime it first. An old deck like yours will peel in a year, then you have bigger problems. If you want to put a color on it, Two coats of oil base stain will last. A solid color stain also requires an oil primer first. Oil sucks to work with but lasts longer.