There’s a company near me who sell gas struts of all different sizes and strengths.
I bought a couple for the front boot lid of my fibreglass campervan which had basically no umph in them from new and just went worse over the time. Disappointing really, given that you don’t open and close a campervan boot lid that often.
When I got the new ones I had the choice of strength and chose ones that were about twice the resistance of the old ones. (didn’t want to go too strong as it’s only a fibreglass boot lid which is a bit bendy and flexible.) Anyway, just a couple of years on and still not that much use, I feel like these struts have lost there initial umph.
Maybe it’s just crappy quality I don’t know as I haven’t looked at the label which is likely to tell me it was made in China, but I do suspect that may be the case.
I owned a 98 Falcon wagon for four years and a 2002 Falcon for nearly ten years and used them daily lifting their tailgates many times throughout the day, and never had a problem with the struts.