How do they verify the degree of your opiate dependence? I mean what keeps people from exagerating to get more methadone?
There are diagnostics they use to verify the severity of your use, or more specifically, how severe your
withdrawal is. Being in "visible" withdrawal is generally a requirement for being inducted onto either Buprenorphine or Methadone maintenance. Symptoms such as teary eyes, runny nose, goosebumps, tremor, dilated pupils are observed by a clinician, whereas other symptoms like vomiting, gastrointestinal issues, anxiety are self-reported. These symptoms together are tabulated into a score, the score will indicate how much you are started on and later, by how much and at what frequency your dose is increased. The starting dose ranges from 10mg - 30mg based upon your score. Where I'm from, inducting at higher than 30mg is pretty unheard of.
While inducting after your initial dose, every few days you will be raised by either 5mg or 10mg, yet again, based upon how you score. You will get 4-5 of these increases before you are at a "stable" dose. From this point on, you will only be able to raise your dose every week or so, generally after speaking to a clinician/counselor. To answer your question about people bullshitting the system for a higher dose, yes, it happens all the time. You will encounter individuals who take 200mg+ daily. A very small sub-section of patients may require such high dosages, but most don't. It's both a fault of the patient for chasing the buzz and the fault of the clinicians for letting it happen.
Clinics only dose during the morning hours. The latest I've seen a clinic open for dosing, is 12:00 noon. There are counseling appointments and groups throughout the day though. Don't count on getting take-homes or carries. Methadone Maintenance is notoriously strict. Generally, 3 months of clean UA's, no absences and kept appointments will net you 2 days weekly of take-home medication. 3 more months, will get you more and so on. Medication is generally not given in pill form, but as a liquid, in sealed bottles.
Your Oxycodone habit is not prolifically high, so I wouldn't expect the induction process to be very uncomfortable. Only go the route of maintenance if other means have failed you completely in the past. It is a major commitment, not to be taken lightly. The clinic will take up large chunks of your life.
I forgot to add, this is speaking only for how things work in the USA. As I understand, things are a lot different in Canada, Europe and etc.