Have you played around with foaming TPU or Morphlex? Both could speed up your print time and allow you to control the shore hardness via flow rate, nozzle temperature and infill.
I havenāt really tried the morphlex. I googled it and it looks like also the material to use for this type of application. TPU has worked good so far in other projects and it is inexpensive material to use. I paid 18 euros for 1kg roll.
Not in ja hurry really and slow printing process is sometimes just mesmerizing to watch
I remember when I got my first FDM printer many years ago I would put a chair in front of it and just watch it print for hours; still do sometimes. 
I take time lapse videos of my prints. Those are fun to watch.