Battle of the Stains – Penofin vs. Cabot

Because Price Point and Quality Matter
–For Penofin, what is recommended at the 3rd year?  Is there another complete redo after year 7 or so?
With Penofin, once the product is applied the first year with two coats, the protection should be there for around 10 years (via Woodsmith Store & Online Forums/Research).  The color is what we will want to control throughout the years.  After a few years if you notice a few “walking paths” where the color is fading, Penofin can be used to “patch” certain areas up to rebrighten just those areas.  A quick wash is recommended about once a year (with any product) to keep dirt from sitting on the deck.  Low Pressure Washing will clean off the year’s dirt and brighten the color of the deck, which makes the color of the stain last longer.  Once a deck is done with Penofin, there should never be a need to do a complete redo.  In year 4-5, a softwash clean of the deck needs to be done and then the only one coat of stain/seal needs to be applied.  No stripping or hard washing needs to be done (which is hard on a deck in general).  The labor rate goes down because of less labor to do the actual job and the amount of material goes down cause you only need to recoat with one layer.
–For the Cabot, the recommended approach is to completely redo every 3 years?  So, in 3 years, we would be looking at the approx $2600 again?
That is correct – to a point.  Vertical  surfaces with either kind of stain lasts about a year or two longer than on horizontal surfaces.  Cabot stain is a surface stain.  Once a surface stain fades away, you have to strip to bear wood and restain.  If you do not strip the wood down, the existing stain that doesn’t come off in the wash will be shiney compared to the bear wood where the stain would have soaked in.
–So each product is a seal and stain in one?  Or are there 2 different applications…for a sealer and then one for the stain?
Each product (Cabot and Penofin) is a seal with a stain or toner all in the same product.  Penofin has a tinted seal (available in multiple tinted colors).  Cabot is either a tinted seal (toner), semi-transparent, semi-solid or solid stain (depends on the amount of wood grain you want to see).  Cabot is applied with one coat, Penofin is applied with two coats the first year – after is one coat.
–By properly protecting the wood, given our climate, do you have any numbers on the life expectancy of our deck/fence?  Is the life expectancy different between Cabot/Penofin, assuming that the proper maintenance path is followed?
I cannot give you any life expectancy of any wood in our climate (too many variables – surrounding vegetation, amount of sun/day, humidity via the ground level of the deck, etc).  The life expectancy will be much greater with Penofin than Cabot though.  The reason is Cabot penetrates into the wood about 3 layers and the Penofin penetrates into the wood about 7-8 layers.  The deeper the penetration, the deeper the protection of the wood from mildew, rotting, old age. 
Check out this website for and click the flash for a short video sample.