You may find that if your teeth have not relapsed too badly and you only need some minor adjustments, there is an Invisalign lite option. This option is for milder cases and therefore it will require less time and will cost less too. Do consult your orthodontist for an assessment first.
I recently saw a lady in her 30s, much similarly to yourself, she was too busy as a working mum to bother with her retainers and her teeth gradually become crowded again. It is very important that the current condition of her teeth, gums and roots are checked before re-starting orthodontic treatment. This is because, when you have braces the first time, root shortening may occur. This can be made worse when you wear braces the second or third time. Therefore for my patients who require a re-treatment, I often go through vigorous checks to ensure the optimum health of their teeth, gums and roots prior to start of treatment.
Lastly, please do note that even after treatment for the second time, you will need to wear your retainers long-term. You may even ask your orthodontist to consider a fixed retainer if you feel that you may not be disciplined enough about the removable retainers.
Good luck!
