I experienced it recently. I submitted batch of 38, 16 and 11 images to DT, DP, 123rf, FT.   Except FT, all other sites are running very slow in terms of review times. Some of the uploads date back to 18th Jan,  The files are pending and status does not change. or sites are picking up fewer files to review and while others are just pending.

Whole this market of Microstocks removed fear from my mind.  Now I know two or three things which keep me cool. First, upload and forget.  Second, Never mind rejections, some sites are picky and choosy while others are liberal. Third, do your job nicely and improve.

The last, just go on uploading.

Recent times have not been better.  Anyone experiencing the same phenomena at this time of year. istock exclusives are coming home. That may be a reason why reviews are late. 

I seriously think, there are low-earners microstock sites which delay the review period just to sound like exclusive and premium among the others.  Bad examples are easy to copy and some microstock sites are competing very hard and wish to be seen as fore-runners in the pursuit.