Tarifx.geo - Creating multiple georoutes - r

Question

I'm not sure what I'm doing wrong. I'm trying to find the drive time between many zip codes. I am able to do so with ggmap, however the API load limit is 2,500. I need to run this for more and heard that Bing can help. I tried using tarifx.geo, which works for a single zip to zip drive, but I need each zip combination individually listed. Lets get to the examples:
Google:
require(ggmap)
from <- as.character(c("27205","48212"))
to <- as.character(c("54952","14450"))
driveTimes <- mapdist(from, to, mode='driving')
print(driveTimes)
from to m km miles seconds minutes hours
1 27205 54952 1533077 1533.077 952.654 52716 878.6000 14.643333
2 48212 14450 555906 555.906 345.440 19700 328.3333 5.472222
^^ Notice the two drive times
taRifx.geo
When I use tarifx.geo, it looks at each zip code as a waypoint along a trip.
require("taRifx.geo")
from <- as.character(c("27205","48212"))
to <- as.character(c("54952","14450"))
combined <- data.frame(from, to)
combined[] <- lapply(combined, as.character)
for (i in 1:nrow(combined){
driveTimes <- georoute( c(combined[i,1], combined[i,2]),
verbose=TRUE,
returntype="time",
service="bing" )
}
print(driveTimes)
time
1 21040
^^ Here I need it to print two rows for each zip to zip drive time.
Thanks in advance for your help! I've tried several methods defining the from/to, but I might be suffering from lack of sleep and can't see the problem right in front of me. If there is a better solution, please do tell. :)