Yes, a breast lift and tummy tuck can certainly be done in the same surgery.
The obvious advantage of that would be :
Cost savings - you will be almost doubling the facilities costs if you do them separately
One less general anaesthetic
Savings on "down time" - don't have to put aside time for recovery twice.
The other less apparent advantage are :
Scarless breast lift - if you only need a minor lift that can be achieved with a properly selected implant then your breast lift is scarless as it can be performed via the tummy tuck scar
Other procedures for less - tummy tucks are very often done with some liposuction. The fat from the liposuction can be used for grafting for face, breast or body contouring at very little extra expense
Tummy tuck with implant breast lift can be definitely done under 6 hours by a single surgeon. That said, it is still considered a long surgery as for as cosmetic surgery goes so you will need a proper assessment before surgery.
Hope this is helpful.
Best wishes
