BJ is correct, the remission rate published stats are for newly diagnosed cats whose first insulin is Lantus.
I would like to invite your vet to look in to Levemir, aka detemir, for you. As a first insulin in cats its remission rate is just as excellent as Lantus, but as an insulin replacing a previous insulin such as PZI, ProZinc, Vetsulin or Caninsulin it has achieved remission after 2 years on the previous insulin! Member Sheila, Beau & Jeddie had Beau go completely off insulin after 2 years on Vetsulin and only 3 months on Levemir. I'm pretty sure there have been others, but their board names escape me now.
I switched Gandalf to Levemir after 2 1/2 years on PZI. Although he never went in to remission on it, I feel that was probably because of my lack of understanding about how Levemir worked for him at the time (2007) and my horrible work schedule which didn't allow me to consistently dose every 12 hours. He got his energy back after switching to Levemir though and he lived another 4 years while using Levemir, despite other health problems not caused by diabetes.
Lantus may be able to achieve remission for a cat that's been on another insulin for 1 1/2 years, though, I'm just not aware of any members who've switched and experienced that. If there are members who have had OTJ happen after more than a year on a different insulin before switching to Lantus, I hope they will speak up. Either insulin is excellent though.
Here's a basic article about Lantus and Levemir differences your vet may want to consider, although the article is meant for human diabetics.
http://www.diabeteshealth.com/read/2007/07/17/5316/lantus-and-levemir--whats-the-difference/
Here is a dissertation from the University of IL about Levemir (detemir) and Lantus (glargine)
https://www.ideals.illinois.edu/bitstream/handle/2142/16049/1_Gilor_Chen.pdf?sequence=3 They may be a lot of terms you won't understand, but your vet should. It is in PDF format, so you will need to be able to read pdf's on your computer, but it's also easy to print out.
There is also some info from the University of Queensland about regulating with Levemir or Lantus that is good to give your vet also:
http://www.uq.edu.au/ccah/docs/diabetesinfo/link4.pdf Also a pdf document. And the tight regulation protocol followed successfully on FDMB as well:
http://www.tillydiabetes.net/en_6_protocol2.htm
And here is an ACVIM abstract from 2009:
http://www.felinediabetes.com/phorum5/read.php?15,1778958
Although it states there are no long term studies, Gandalf had been using Levemir for 2 years by then and others longer. The first cat to use it in Europe, Jocularity, whose owner Steve has been instrumental to this board's development and also the Pet Diabetes Wiki, had been on it for 4 by then! Jock's case history with Lev is here:
http://petdiabetes.wikia.com/wiki/Case:Jock There are other case histories for cats using Levemir on the PDW, but none as detailed as Jock's.
If your vet would like to speak to a practicing veterinarian who is familiar with detemir, the vet mentioned in the dissertation, Dr. Thomas Graves, practices in Chicago, here:
http://furnetic.com/about/meetourstaff.html .
Any other questions regarding Levemir, please visit the Levemir ISG here:
http://felinediabetes.com/FDMB/viewforum.php?f=10
Sorry for all the links, but I hope you find them helpful and informative.