[cem] Using CEM with Panel Data in Stata

Hi all, I am using CEM on a panel dataset with the k2k option. I am currently matching observations by year (and a few other covariates). I was wondering if there are any econometric problems while running regressions (post matching) with a matched sample which contains the following situation: in year t observation_1 is matched with observation_2, but in year t+1 observation_1 is matched with observation_3. That is, in different years the same firm is matched with different firms. Thanks, Nel