Hi,
I have got lots of really good ideas of places to visit in Laos from this forum, but now I think I want to go to too many places!
How long do you think we would need to cover this route without rushing too much? We will be there in April or May next year (as part of a RTW trip). We will probably have about 3 weeks, but can be flexible.
Huay Xai (and Gibbon Experience) -Luang Nam Tha - ( via Udomxai)- Phongsali (by boat)- Muang Khua (by Boat)- Muang Ngoi -(by boat)- Luang Prabang - Vang Vieng - Vientiane
I would also love to visit the south on our way to Cambodia, but I think we might run out of time and have to fly there from Vientiane. Also I think the North will be cooler at this time of year than the south?
Any comments or tips on the route would be much appreciated.
Thanks.

I think 3 weeks for this route is fine, no need to be too fixed for time. You may be able to get to Phonsavan after LP and before VV.
Both north and south will be very hot that time of year, take your pick...

As above, 3 weeks should be just about right for such a route without having to rush it.
Don't forget that you'll have to go by road from Phongsali to Hat Sa to catch the boat down to Muang Khua and beyond.
And finally, you'll have the option of flying from Vientiane OR Pakse in southern Laos to Siem Reap if you're running out of time.