How many can be used at once?

[timc2011]

Hello,

I understand that one isn't to use 2x 4G B/D hybrids at once during the acquisition phase. However, is it possible to listen to one 4G (B/D) hybrid at night and listen to a previous one for an hour during the day as a kind of "maintenance dose"?

Also, are any of the 4G B/D hybrids expected to be upgraded to 5G, particularly those developed for men? It looks like the effort is to get the 3Gs upgraded to B/D first.

Thank you,
Tim