There is a good thread somewhere on the articles forum called: 'My Experience with Sustanon' by OTH that addresses the timing issues of the different esters. Worth checking out if your going to use sust. His conclusion is basically that sustanon is not the best testosterone preparation to use for bodybuilding purposes (as it was designed for clinical HRT use with less frequent injections) unless you use it in a way that provides more stable blood levels.
Copied from another site:
Sustanon 250 is an oil-based injectable containing four different testosterone compounds: testosterone propionate, 30 mg; testosterone phenylpropionate, 60 mg; testosterone isocaproate, 60mg; and testosterone decanoate, 100 mg. The mixture of the testosterones are time-released to provide an immediate effect while still remaining active in the body for up to a month