It certainly won't hurt, and there is no reason why not - but it is not going to help your SEO.
On a crude level, what is being suggested would mean that any .uk domain (two year registration only) would have a built-in advantage over any .com domain that is renewed annually (my guess 95%). Likewise, it would mean that a .com registered for three or more years would have a built-in advantage over any .uk domain.
Now, you will say that Google is not that stupid - and I will be the first to agree. But by the same token, they are not going to be so stupid as to put the vast majority of .com domains that are set to renew annually in perpetuity at a disadvantage to those registered for a measly five years.
Tedster on the ball, as usual.