Oh to be young again, Agari, and be so certain....
Yani
Yes, the dimensions do change. Ther following, for example, from the Canadian AIP (on line)
2.7.1 Low Level Airways
Controlled low level airspace extends upward from 2 200 feet AGL up to, but not including, 18 000 feet ASL, within the following specified boundaries:
VHF/UHF Airways: The basic VHF/UHF airway width is 4 NM on each side of the centre line prescribed for such an airway. Where applicable, the airway width shall be increased between the points where lines, diverging 4.5˚ on each side of the centre line from the designated facility, intersect the basic width boundary; and where they meet, similar lines projected from the adjacent facility.
LF/MF Airways: The basic LF/MF airway width is 4.34 NM on each side of the centre line prescribed for such an airway. Where applicable, the airway width shall be increased between the points where lines, diverging 5˚ on each side of the centre line from the designated facility, intersect the basic width boundary; and where they meet, similar lines projected from the adjacent facility.
Have a look at the AIP of the country that controls the airspace you are interested in. It may be a time-consuming task, and you may not get the answer, but you will learn some stuff on the way.
I lost my link to the ICAO docs on the Danish Government website, but you may find good info there.