hi, this is my very first post =)

i was diagnosed with adhd inattentive type recently. i started out with concerta for a month, it really worked well in the beginning but i noticed it wore off later during the night when i had to study (probably cuz i took it like five in the morning for school!). but later on i had urinary retention and constipation so dr put me on focalin xr 15mg.
it was my first day on it. it definately was way more smoother but i duno about the focus part. im trying to study today but im getting very distracted. but one questoin. why the heck is there an expiration date on the focalin xr? it says discard in a year, i compared it to my concerta and that one doest have any discard date..do you guys know why?!??! its mind bogggling...whats gonna happen if i take it after the date? won't work?