You can have the strings shortened
I stuck it out and ended up only having a period every 3 month's and it was so light I only used liners and I kept it in for almost 4 years and loved it.
I don't recall how long it took to settle though but I went from long heavy painful periods pre mirena to only a few light ones a year so big win for me

Sent from my Galaxy S3 so please excuse errors.