I'm continuing my allocation to VGSIX (Vanguard's REIT Index Fund) per my AA.

I first bought in  last year when the price was down (I also bought into VPACX, Vanguard's Pacific Index Fund which was also down last year).  When VGSIX was way up earlier this year, I rebalanced my AA by selling some VGSIX shares "high."  Now, as it falls, I'll be rebalancing, which will include buying "low" additional shares of VGSIX sometime soon.