How best to use DP slots: 3 DPs together or spaced out

Since we're in the doldrums of transfer rumor season, I was just thinking about how, if we're NOT going to use buyouts on any of our DPs, does it really make sense to sign them so close together? Or would it be smarter to space them out and sign a DP every two or three windows? You'd always have a DP spot about to open up. You'd never be in a situation where all three are locked in and underperforming and the situation looks completely hopeless because one of them would always be out of contract soon. You'd also always have two that are very settled at least. Does anyone have thoughts on which strategy might be better?