It depends on how you worked doubling the recipe. Is your lasagna now twice as thick (deep) or in a pan twice as large?
If it's in a pan that is twice as large, then you don't have to increase the time overmuch, maybe just 10 minutes or so. But, if it's twice as deep, then I would increase. However, just don't assume you have to completely double the time...it may be done in 20 additional minutes...or it could take twice that. I'd start checking at an hour, and go from there.
How can we sleep while our beds are burning???