Which frags???
The blue ones I do about 50/50... I have cashed them in for a soul here or there... but I'll also spend on the awakening runes. Especially the lower priced ones.. you get more for the 200.. and you are as apt got the the 5 star stuff from the 400frag soul as you are from the 1000frag purchase.
The purple/burgundy ones... I've not cashed any in for a soul at all. And have spent all those frags in the store on stuff.... From W LOL initially to other items. Saving now for either S LOL.. or whatever comes at the end...