I've got an SLX30 that is coming up 3 years old and for the first two years I used it as a 20ft most of my work including older 3 floor farm houses. But for a few jobs I needed 25 or 30ft and so just added those sections when I needed them so that I wasn't lugging a 30 footer around unnecessarily.
After about two years the 20ft sections were starting to wear and so I bought an SLX22 (which I use as an 18ft) and keep the 30ft pole for 3 storey work.
I think in about a years time I might buy an 18ft SLX and so have 3 quick to use poles at my fingertips.
But with cost as an issue I just bought the longer pole and broke it down.