Winter Thermal Cross-Country

Not to stray too far off topic here, but what makes for "legendary"
thermals?

I've been a glider^H^H^H^H^H^Hsailplane pilot for two years now and
have already enjoyed some wonderful thermals in the southwest (USA).
But I think I've had only a few that averaged 10+ knots for more than a
few thousand feet. (I've had a couple that averaged ~8 knots from 1500'
to 15000'.) A fellow rASAr once told me about a 30-knotter he
experienced but that was over a fire (does it count as a thermal as
long as it's adiabatic?). I've heard about 20-knot thermals in northern
New Mexico; are those rare or routine?

The best general lift I've ever experienced was under a cloud street
south of Ely. It was so strong I had to divert to the edge of the cloud
line a few times. It was the first time I got to experience a long
stretch of fighting to keep the altitude below 18,000'! Needless to say
I can't wait to visit Ely again.

~ted/2NO