If you were going to store a user agent in a database, how large would you accomdate for?
I found this technet article which recommends keeping UA under 200. It does
I got this user agent today, overflowing our vendor's storage field:
Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; MDDR; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Ridiculous! 229 chars?
So take that size, double it, double it again, and you should be set until Microsoft's next blunder (maybe this time next year).
Go bigger than 1000!