Honestly... I think Yamato is trying to cashing in at their soonest.
My opinion, they should give a decent space between releases with reasons
1. it give time for them to perfected the design and avoid QC issues because rushing to release the toy
2. It give us, one of their biggest customers, time to put aside some money
With short timeline between the release of VF-1S Hikaru, VF-1J, Fast Packs, YF-19 FP (not sure..) for example, instead buying all of them, I have really to decide to buy either one or two... what a pity To pick up at later dates... prices might gone up already come on Yamato