I need to do this too. Any recommendations on a good sealer. One I don't have to apply every two years.
That product does not exist. With the way the wood expands and contracts with the Iowa weather it just isn't possible.
Prep of the deck is the most important step of a good deck restoration. You should use a detergent that will break down gray wood fibers on the surface for easy rinsing. Depending on if your deck is stained currently or not you will want a sodium percarbonate or a sodium hydroxide based deck cleaner/stripper. The step that is always skipped is neutralizing the deck/ground with an oxilac or citric acid. These does several things 1 it brightens the wood, 2 it helps open the pores of the boards up to accept new stain, and 3 it neutralizes the 10+ ph cleaner/stripper you just put on your deck and surrounding ground.
Next step is to let the wood get below 20% moisture content, depending on the amount of shade, weather, other factors this will take between 3-7 days, if it rains the clock resets.
Picking a stain is also important I recommend only oil or water based semi-transparent stains. There are tons of good brands out there that will run you between $25-$50 per gallon. You don't want to use paint, solid stain, or any type of acrylic stain. These types of finishes are very difficult to remove/maintain.
http://www.olympic.com/products/stains/13/olympic-maximum-stain-sealant-in-one
With a good oil based semi transparent you can maintain the flat surfaces/traffic areas every 2 years, and rails every 4-6. The key is to do maintenance before the stain starts to fail, once it fails in order to do it properly all the stain must then be removed to apply a good looking new coat. These finishes can also be easily removed without using extremely dangerous chemicals that is harmful to people and plants. So if you don't like how it looks you can somewhat easily change your mind.