From my observation, some professors who took 3 months are either hesitant to write you a good LOR or being so lazy. Dude, I've experienced one professor who wrote me one with in a week. They should also know how relevant LORs are..duh they've been in college too. When that happens again you should look for a super alternative professor that would write on your behalf asap.
Also when asking for an LOR tell them how important it is for you and that you have chosen him among all other professors...which kinda makes him special. Also remind him that there's deadline and that you appreciate him if he writes a letter asap. I had to do that to all of my professor...actually I gave them a signal on my final after my exam telling them that I'm making them as my option to write me an LOR. Most of those who said yes wrote the LOR pretty fast when I sent the electronic email request. Also I dropped by the office and gave them my personal statement, extra curricular, volunteer and the class course I've taken with him/her so they can write more about me lol.
