There is a lot of FF availability from DEN-LGA. I looked up 3 sets of random dates in April and May and most days had at least one flight available and sometimes two. Those days not having availabilty did have seats during the same week. (the award calendar will show availability on surrounding dates if your initial date request has none).

My personal experience redeeming awards has been very favorable, although it's not quite as easy as it used to be. Early Returns is NOT nonepass.