According to Steve, he has enough "old stuff" to record several albums. He is to be believed on that matter, as his four contributions on the last one show he is not short of ideas. One must also remember that he didn't write When the Wild Wind Blows during the FF sessions, as he had written that song long before and kind of lost it somehow; he just had to arrange it. So he tends to write musical themes and melodies all the time, but only turns them into proper songs when they have dcided to record an album.
The main problem in my opinion is the way he finishes the songs. Since 1982, he wants to do it in a short time, thinking the pressure is good for his creativity. No wonder it's becoming more difficult with time. Back in the 80s he was writing at night, until very late, and we know his schedule during the last album sessions were quite intense. He is ot looking forward to imposing such a burden on himself, but he will do it ultimately.