Pex manufacturers require support every 32". It sounds like you don't have much support. As with every piping install the more joints you have the more leaks you may get. I'd try to keep the tubing as intact as possible keeping in mind that pex shouldn't be ran stick straight or tied down hard. Because of the expansion contraction the pex pipe should be supported well but allowed to have some movement, sagging is common but if it's well supported it shouldn't be a problem.