I replace shocks every couple of years. When you can easily retract and extend them by hand when new, I question how effective they actually are on a piece of heavy equipment with heavy axles and tires. They don’t appear to be any different than shocks for a .. Toyota Prius or other minuscule light vehicle.
Only factory. Whatever Volvo uses is what I used on it. Funny at the dealer they were as cheap as anywhere else. Now freightliner same thing. Sachs is what they use. Never had any luck with Gabriel or Monroe. I replace them every year on steers and 2-3 on drives. Also run centramatics all around. Gabriel HD I think came close but even those leaked. also carry a spare or a set at all times. That way when they do go out and leak you paid the best price and aren’t at the mercy of a shop. TA for example is insanely overpriced. Same with loves. I watched a guy pay $90 for a garbage shock I know could be bought on Amazon for $48. easy to replace yourself. Need an impact and an open end wrench.
I’m restoring a 1965 White right now that still has some Delco shocks on the steer axle. I’m just repainting them and leaving them on. Back then shocks were an extra cost spec that had to be added on with many trucks. With 12 leaf stacked springs shocks are useless in function anyway. Delco hasn’t made heavy duty truck shocks since the late 80’s when GM got out of the heavy truck biz.