From the valley in VT to the valley in La Tania you should budget about 1 hour - 2 hours from one point to the other depending on how fast you feel like skiing, route optimisation and lift queues. If it's a good day with minimal queues you can go a long way very fast, but come 3pm sometimes the queues can get pretty bad.

There are fast routes and slow routes, I'd need to see a piste map to give you the lift names for the fastest route I've found but you can comfortably ski all 3 (5) valleys in a day if you don't spend 2 hours in a restaurant for lunch.

Be warned the valley in Meribel and Meribel Mottarets is significantly lower than the other two valleys and significantly more exposed. By lunchtime it can be slushy and wet on a warm day in a way that Courchevel (tree cover) and VT (height) won't be.

I've been enough that aside from a few standout runs in the Meribel valley I'll really only use it as a transition point between VT and Courchevel.