You're stating that you have sleeping issues, and I take it that you have been prescribed Seroquel specifically for this matter. If this is the case, then it is in my opinion not a bad choice, though some would argue there are better(safer) options due to the risk factors involved with the class of drugs to which Seroquel belongs. There are a number of other(*safer*) drugs that are being prescribed for sleeping issues which includes antihistamines such as Atarax/ Hydroxyzine or Phenergan/Promethazine or small doses of tricyclic drugs like Doxepin/Sinequan, Mianserin/Tolvon and many more.
Now, I have taken Seroquel for severe sleeping issues for almost 2 years. It has extreme sedative qualities and works very well in small doses. I'm currently taking 12.5 mg every night. What I like the most about this med is the short half-life(appr. 8 hours) and that it leaves the system quite quickly. Besides from the pleasantly short half-life it is more or less void of any tolerance development to the sedative effect at low doses.
Have you taken seroquel nightly for 2 years without any tolerance to the sedation? If so, thats fantastic news because I think it is the best med. I have tried for my insomnia. I am on the same dosage as you too so that makes me feel hopeful as I do not want it to stop working!