Thanks very much for your replies much appreciated.
It looks like ill be going for the deore rings after your comments, interesting what you say about the big(ger) chainring9s) as i always thought grinding out bigger gears lead to more wear, what with the chain running at increased angles. At the moment the rings are 22,32,44, but i may go up to the higher tooth possibilities if it would increase longevity.
When i say that i do touring i mean very long distances (last ride = Alaska to Argentina) and im getting ready for norway to new zealand via the Stans and tibet, as such i need things to last due to spending alot of my time on dirt roads in less developed countries where getting old of quality replacements is a full on drama ( i had to wait in bolivia for a tyre to come via a friend in the US for three weeks, three fu==ing weeks). If anyone has more to say about the bigger toothed options i would be keen to hear opnions.
Thanks very much for your help, its really is appreciated.

Rich