How long does it take for a SPV to intermittently sync (order of magnitude)? Say I have a device that is mostly offline, with a SPV on it. 

Say once in a while (for instance once a week) I go online for about 20 minutes, and make a large number of transactions (which are based on transactions I might have received while I was offline). 

How long, would you say, does a SPV (e.g., BitcoinJ, bitc or  others) need, upon getting online, to be fully operational in these circumstances?

I confess: I am not yet familiar with SPVs (although I did read about them, I have not had time to fully understand them yet). The steps a SPV follows to sync are outlined here, but no timeline is given. 

Thanks
SPV syncing depends entirely on the SPV servers that you're connected to. They may not have that much bandwidth and you might have a very slow sync, for example.

That said, you only need 80 byte headers per block you haven't seen (about 1000 blocks per week, or 80Kb for every week that your device is offline) and about 500-1000 bytes per UTXO you have (obviously this is highly dependent on how much new UTXOs you've received).

So assuming about 5 tx's per week and 1000 blocks per week, it's less than 100kb download to catch up once a week, which by any measure should be very quick. On most connections it shouldn't take more than 10 seconds.