As mentioned above the problem is that when you modify the description on the item card it affects many other tables, reports and variables in the system
If you miss updating any of them then when the system tries to fit the bigger text string into that smaller variable it will fail with an error
You have several possibilities,
Add a description 3 field, this will not be used anywhere so you can add it where needed with up to the maximum length, you could possibly hide description 2 and "replace" it with this one on the item card, that way they only see the main description and description 3
Rather use dimension to categorize the items, instead of a longer description, the positive spin off is that you can then report on those dimensions
Last option is to customize the description 2, but brace yourself for a huge amount of work and a pretty broken system until you find all the spots that it is used
Cheers
Nev