If they are pulsing, they are not fully extended.
We use a tape measure to get it purrrfect. the manufacturer does not specify that there is a correct position to install except fully extended. I have not seen an oring fail yet. I have seen them fail when they are in a bind, when they are not fully extended, not enough pipe glued on, or they were the brand at ace/lowes sells(the type that disassembled seems to be more prone to crack).
But i agree with you especially on pipe bigger than 1", 4 90s is preferable.
On a side not they do make schedule 80 telescoping couplings.