Deca is in the system for 3 weeks; no need to taper, it is self tapering. If concerned about crashes, taper on shorter-acting compounds.
I like deca; I like nandrolone phenylprop even better. For the magic it works on joints, it's (nandrolone) worth the price of admission.
If I'm running deca, I'll run it with test, then cut it out 3 week prior to the test. That way, post-cycle, I'm only recovering from test. This has worked very well for me.
Alternatively, I'll run deca and test up front, then switch to NP and test mid-cycle.