You really should consult a lawyer, because it is complicated.
I received the permanent residency permit about 1 year ago. In order to apply, I needed to take the national language exam (and pass) and the constitution exam (and pass). Both were quite difficult for me.
But even then it was not over. There could not be ANY gaps in my residency. That means that if I had allowed the temporary permits to expire before receiving the next, I would not have qualified. Also, I had to fill out the dates of absence from Lithuania for the past 5 years. I had to list all of my travels, and the dates. I could not have been absent from Lithuania for more than 2 months per year and (I think) 10 months over 5 years. These conditions are constantly changing. I recommend to consult a lawyer and get more accurate advice.