It's a waste of time if you could have been living a better a existence and have been building on a better experience. The prospect of death is still looming, if you haven't prepared yourself, you may still die without having your affairs in order for cryopreservation and you might take a nihilist stance in life that ends with you dieing before immortality is achieved and worse yet, you never got your cryonics plans finalized and funded.
The rest of your statement is good though.
"The prospect of death is still looming"
I live my life as though I have at least 1000 years to live. Within those 1000 years I plan on living all the lives I could possibly live according to what I know right now. That is to say, live as a doctor, a scientist, a blue collar worker, etc. I could likely cover almost all if not all “fields” of work within those 1000 years. Beyond that there’s different countries, cultures, hopefully worlds and beyond.
Given all of that “waste of time” isn’t such a narrow specific thing anymore is it? If I spent 10 years living my life in doubt/uncertainty only arriving upon an answer at the end of those 10 years can I really call still that a waste of time considering the 1000 years I have to live (minimum)? If I only had 80 years to live though that's 1/8th of my life gone and that IS a waste of time.
I guess my point is that “time” needs a dramatic redefinition when you’re talking about living a truly immortal life. And the prospects of death still looming are an issue but when looming is 1000 years+ down the road should that prospect be as much of an issue?
Under your philosophy cryonics; isn’t it the best to just live your live looking down a 1000 year+ road? Though I wouldn’t call being frozen for 1000 years living; that’s more of a pause button.