Thanks for asking, Barbara - I think the simple answer is "when we can make it financially viable"!
At the moment we're saying that if this all goes as well as we think it will we'll make future plans accordingly. I'd love to come back to the US (either solo or with Mary) but these days I have to be more careful with money (husband and cat to keep fed and comfy, mortgage and bills to pay) so any tour would have to pay its way. But nothing is impossible, I know, so here's hoping ...

Anne