Tire problems/extra parts
IMHO, it depends on how a person drives and what they are driving. The only vehicles I have seen, for the most part, with tire problems are travel trailers and some older 5th wheels. In the past, many of both, tended to be built with inadequate sized running gear, axles, bearings and tires. Plus with the cavernous spaces available they tend to get overloaded very easily. The trip to/from Alaska is no more difficult than any other long trip. Some folks try to exaggerate the road conditions to make themselves seem more adventuresome and macho. (Is Macha a word?) It is a great adventure and the highways are fine, just slow down for the construction sections.(most sections are only a few miles/kms long) If a person would take 2 spare tires to drive from Los Angles to Boston, then take 2 spares to drive to Alaska. Otherwise, unless you have very odd sized tires or pull a trailer, I would only carry the one that came with my vehicle. (Trailers are different IMHO) If you are going to drive the Haul road or the Dempster then an extra tire might be very appropriate.
As with any spare parts, if it makes a person feel more comfortable, then take them. Most often, it is easier to find a mechanic to fix a problem than it is to find the part you need, when not close to a large town. Every vehicle should carry a tire pressure gauge and use it often. Under inflated - over loaded tires are the number one cause of tire problems IMHO. I like to have a few thousand miles on a set of tires before heading north. Not always possible to do. Last summer, we departed with two new rear tires on the truck, very expensive Kevlar reinforced ones. At a campground in Idaho, I noticed a bulge on one of the sidewalls and stopped at a tire shop. Sure enough it was a separation starting and had to be replaced with about 3,000 miles on the tire. The replacement new tire made the rest of the trip just fine.
So much of a person's perspective as to road conditions, is tied to what they are used to using. As well as their experience at driving large vehicles, which most RVs are these days. When someone says a particular road, is the worst they have ever seen, for them that may well be a true statement. When some of the more urban folks, make there first trip to the north country, they may well encounter, their first gravel roads. The main highways are paved, but some of the secondary roads, such as the Top of the World and the Denali Hwy are gravel for the most part. You need to slow down especially on gravel to protect your tires and vehicle in general. Many new to driving a large motorhome, don't seem to understand this concept and want to blame the highway for any damage incurred. The problem is their driving, not the road, IMHO.
I have, for several years, been trying to understand, what it is that inspires folks that have never driven the Alaska Highway, gone on a caravan, taken the ferry, and on and on, to give advice on those subjects and it is always something negative. Don't remember any of the 2nd or 3rd hand stories these folks like to repeat, ever having a positive tone to them. I have a brother in law, not a forum member, who lived in the Banana Belt (Anchorage) for 17 years. They had several campers but never one time drove the Alaska Highway until years after they moved to the Lower 48
This is a very large forum membership site, and I would not doubt that there are not 1,000 or more forum members that have driven an RV to Alaska. A large source of 1st hand information is available. Do the pre-first timers just want to try and fit in so badly they have to quote some anonymous person(s)? Maybe all this fits in the same category of the "big fish that got away" and that some things are OK to repeat whether they are true or not.
I have talked to people along the Alaska Highway, our last 2 trips, that were disappointed in how easy it was to drive to Alaska. They had planned, schemed, read and got themselves so psyched up to think they were intrepid explorers to rival Henry Stanley in his search for Dr. Livingston, in darkest Africa.