I usually carry all my lenses on a hiking trip. I have a EOS R6 II, 100mm macro, 100-500, 1.5x extender, 24-70, and 15-35, extra batteries, filters, lens cloth, carbon fiber tripod, snacks, a gallon of water, coat, hat, and gloves. All packed it’s between 30 and 40 lbs. The key is the backpack. I use an F-Stop gear mountain series pack. All the weight sits on my hips. I do have a smaller sling pack that just holds a body and an extra lens that I use when I’m just going to a park and will only need a couple lenses. But if I’m going on a real trip, I want everything. It sucks and can cost you lots in future print sales to run across an amazing shot and not have the equipment you need.
Yes. Replace them every 3 years.