Regarding the big block, it runs thru a Bravo3 which is a dual prop setup. I am sure that drive and props are not stressed about it.
Changing props every 2 years? Never heard that one. Impellers every two years, sure, and to replace those in an Alpha drive you remove the lower and that is easier to do by removing the prop first, especially if it is stainless as those are heavy, maybe some terminology is getting mixed up in translation. On a Bravo the raw water pump is on the front of the engine, no need to split the drive.
It is a good thing to remove the props each year, and re-grease the prop shaft splines to eliminate the chance of props siezing to the shaft, but even then if greased on the last install then 2-3-or even 5 years maybe good enough but I would not recommend waiting that long.
If you boat in the ocean or salt water anywhere really, and the boat is left in the water for weeks at a time. you need some type of galvanic protection to keep the dissimilar metals in the drive/props from corroding and losing material when they try in essence to make a single cell battery. Two types of metal in salt water when close enough will generate a small electric current, when this happens one metal gives up material and one takes it on, but neither in a good way. Have to replace anodes often, anodes are mounted on the drive or drive mounts and give up their material "earlier" thereby protecting the stuff that is important to not have corrode away on you. There are active electrically powered solutions that counteract this as well, your boat may or may not have this installed. If the props are in salt water and the corrosion protection has failed then they will usually not last a whole season if the boat is slipped all year. So, this can cause prop replacement being needed every season or two for sure, and the drive eventually.
For inland trailer boating, in my opinion good props, especially the SS ones on a Bravo3, should last as long as the engine and drive barring any prop strikes or corrosion issues.