For now, disregard the google results. Unless you have renal impairment (i.e. problems with your kidneys) you likely are not taking enough to need blood monitoring. In high doses the lithium plasma concentration within the body can potentially reach toxic levels. It's simple to quickly check for warning signs of toxicity without a blood test, one method is to simply hold your hand out in front of you and relax it. If your hand begins to you may need to have your blood level checked. I'm not sure where you came up with weekly monitoring, I've gone years without needing to have my level checked. Additional signs and symptoms can be found here: Lithium toxicity: MedlinePlus Medical Encyclopedia.

It's ultimately up to you to decide what you want to do, but I would give it a chance. Some people take 1800 mg a day, at your dosage you probably won't even have side effects. Lithium is just an element, it's the most "natural" of all the pharmaceutical treatments. Stick with it a few months, even if you only feel comfortable taking one of the 150 mg capsules it is still worth it.