The infraction must be filed within 5 days of the time the notice of infraction has issued. Add to this any time the mail system will take to get the infraction to you. If an infraction is issued after this time period, I would consult with an attorney and discuss posssible arghuments to make.
This question has to do with ISSUANCE and not filing. An officer can *probably* issue a ticket up to 2 years after the incident in question. While the limitation for infractions is not expressly set out under statute (and hence I write probably above), civil infractions contain civil penalties that amount to forfeitures of bail to the government, and as such an officer would have up to two years to mail you a ticket.
This answer is given merely for informational purposes and does not create an attorney-client relationship. For specific advice, contact an attorney in your state to see if working together makes sense.