Many conversion candidates believe that a prior conversion will speed up the time of a second conversion. (If you are in the unlucky group that gets to 3+ conversions, you're more likely in the territory of geirus l'chumrah than "normal" geirus.) After all, it makes sense: you've already "cast your lot with the Jewish people," learned holidays and customs, become integrated into a Jewish community, probably even learned some deeper things, maybe even read Hebrew.
So does a prior liberal conversion help you to get an orthodox conversion faster? In short, I'm leaning towards an answer of no.
But maybe the better answer is that I think other factors are much more determinative than having a prior conversion or not. A prior conversion may even be largely irrelevant.
This isn't scientific, I'm afraid. It's just the feeling I get from talking to other "upgraders" like myself. As for me, after a year and a half of being observant and many years of studying orthodox sources, I'm not converted yet, and I don't know when I will be. That doesn't seem to be unusual today.
So what DOES matter?
- Current relationship with a Jew. (If you're in a relationship with a non-Jew, don't even think about approaching an orthodox rabbi about conversion...you will get absolutely nowhere.)
- Number of years studying towards conversion. (Yes, years.)
- Even more importantly, what did you study? Five years of studying primarily liberal sources (especially reform and reconstructionist sources) will give you almost no background for an orthodox conversion. After all, the reform and reconstructionist movements don't view halacha as binding, so few sources discuss traditional halacha. In an orthodox conversion, that traditional halacha is the primary thing you will be learning.
- Where you live. This is the killer for most people. A year lease is a long time to wait to "start" your conversion.
- Integration into the community. They want to see a support system, friendships, the possibility of marriage for singles, etc. Will you be able to take care of yourself in the community and do you have the support system to keep you within the community? People who feel isolated or alienated from the community are the first to leave orthodox Judaism, whether born-Jewish or converted.
Not living in an "appropriate" community and romantic relationships seem to be the two things that will "slow you down" most. In my opinion, those two factors are much more determinative of the length of a conversion than whether there is a prior conversion. Prior knowledge, even orthodox learning, seems to have surprisingly little effect on conversion time. Of course, there are other unpredictable factors that can come up and "derail" you: bullies, being told to move a second time, finding out that a community or hashkafah isn't appropriate for you, health issues, school issues, etc.
Take that for what it's worth, I suppose. I can't give you an easy answer here. Every case is so very different.