Only time a trigger will be disabled is if someone goes in and disables it.
Triggers shouldn't be the first choice, if a problem can be solved without a trigger then it should be solved without a trigger. Check constraints, foreign keys, etc. If there's no other way than a trigger, then use one and make sure it's written efficiently and correctly to handle multiple rows.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass