Walikum As'salam,
Yes you can re-apply with valid LOA anytime.
There is no time bound to reply but it's better to re-apply within this time frame:
For September Intake:
March mid to April end is the best time
For January Intake:
Sept mid to Oct end is the best time
For May Intake:
Nov mid to Dec end is the best time
It vary country to country as well how long CIC required processing time in your county.