Not true. They can be very effective for non-maintence if used properly... A short one month taper on either methadone or bupe can be really benifical. The doctors and shit make it sound like those meds can only be used and should only be used for very long periods of time, but that's just because they are greedy bastards and want you to keep paying every month, more so with bupe.
I don't see how switching one opioid with another opioid could provide any benefits. Especially when methadone, buprenorphine and other synthetics sometimes have more severe and more drawn out withdrawal symptoms. Opioids at least IME provide very little relief compared to benzodiazepines when tapered. At least for me, it's just a question of suffering withdrawal now, or suffering it in a month. As you probably know opioids have the highest relapse rates of any drug, so maintenance drugs are there to cater to that.