PE Secondaries

Have been thinking about PE secondary sales (Harvard, UVA, etc.). And have a thought - assuming PE returns are largely a function of vintage, and assuming now is the right time to begin putting money to work, could it be that the sellers are actually not exiting PE but rather freeing up capital to invest at the right time? For a public stock, future beliefs about the industry or asset class determine whether to hold or sell a position, regardless of prior losses. For PE limited partnership interests, different years and funds are not fungible and so investors need to make a new purchase to get exposure (can't simply hold on to old investments and ride out the volatility). So, although there may be some increase in value for 2006 vintage funds, better to get in the 2009-10 funds even at the cost of writing off a large part of the value of recent investments. Just a thought.