Long delay in review process

I also have some images waiting for more than 9 months. On 2 different occasions recently, I resubmitted a couple of them and deleted the old ones. They still haven't been reviewed after several weeks... 

Sure, others are facing the same deleys. It is simply that the moderation is overwhelmed currently with submissions. And there is a chance that your assets are "stuck" in the moderation queue, and they won't be offered to the moderators. 

My guidence would be to delete some and resubmit and let some in the queue, so that any decision you take is not the completly false one. Don't delete the assets before you have secured the metadata, like keywords and the title.