Time to upload is probably not a problem, you gradually add to it over time. Time to download all the data in the event of a disaster is the bigger issue. There aren't a lot of use cases where you'd need all the data back ASAP but if you have such a case, don't rent this storage.
10TB == 10,000GB == 10,000,000MB
10Mbit == 1.25MB
10000000/(1.25 * 60 * 60 * 24) = 92.6 days
Time to upload is probably not a problem, you gradually add to it over time. Time to download all the data in the event of a disaster is the bigger issue. There aren't a lot of use cases where you'd need all the data back ASAP but if you have such a case, don't rent this storage.