I'm not sure stera but I suspect at least a couple of years unless it is specific to redcurrants only. but why not ask the RHS advisory service. If you are not a member let me know and I will ask for you.

I'm not a member - that's a very kind offer, thank you!
I know it affects redcurrants and gooseberries but I don't know if blackcurrants are vulnerable as well. I also have a couple of young Jostaberries which are not into bearing yet. I don't know how it spreads, ie how far away other bushes can be affected. Its a big blow.
I don't have any photos - the damage appeared in the summer. But the new growth appears to be badly affected and much of each stem appears to have most of the leaf buds dried and brown.
I could photo that if you think it would help. One cordon had to be removed altogether last year and the remaining two have had it.

do you have any photos of the symptoms that I could use. if you have I will send you my email so I can ask the rhs on your behalf.

I didn't take any when the leaves were dying in the summer but if a photo of the pathetic sight now would help i'll take one or two. I believe the disease is called cane blight.

Cane blight seems to infect raspberries.

so any pictures will do to help.