Anything over 39 or 40 feet is a good canidate for a tag axel. It provides better weight handling and road stability. A tag allowes about 10,000 more capacity over the added weight of the tags themselves. A tag will probably reduce the fuel mileage a little, but the added stability and weight handling will override. If at this class and size of a motorhome you are going to worry about the slight added fuel mileage then you should look at a smaller more fuel effecient motorhomes and sacrafice the size and comfort the larger motorhomes offer. We are extended travelers with a 45 ft Travel Supreme DS 14 and love what it has to offer in size and comfort. The tag is a must on larger motorhomes and yes it adds 2 more tires to replace, so what as they last 7 to 10 years. That would have a cost of about $150 per year for tag tires. If the money is that tight then cut a couple of meals out each year to cover the cost. Consider going full time and eliminate the cost of an empty fixed home to one that moves to new places. The cost of living and traveling is reasonable.