Please let me rephrase what I wrote in that post:
I didn’t literally mean that they’re good only for 2 weeks, I said “a couple of weeks” but actually I think I gained from them in a period of 2 months maybe. The initial gains were quite amazing - unfortunately I didn’t do much measuring back then so I couldn’t say exactly how much, but I assume it was close to 0.5 inch in about 2 months time period. I was really enthusiastic at that time and thought that in this rate I would gain much more soon, but then I got into a long plateau (something like 4 months, until very recently) which made me realize that my unit got used to the horses and after about 2 intensive months it didn’t get as pumped as it did in the beginning and also the gains stopped.
So basically what I’m saying is that - as any other exercise - there’s usually a big gain at first when your unit is having to cope with something new, and when it does get used to it the gains either stop or get much slower.