Collecting Addresses for Save the Dates

So we are sending out our save the dates this month (goal is to have all of them sent out by end of January). Trying to collect addresses from FIL’s and FH has been like pulling teeth. I’ve been asking for months and have yet to receive anything, but feel bad to keep having to ask so frequently since I know they have lives. But now it’s January and I still haven’t received anything for addresses from them. My FH says he’s reminded his parents again but I’m worried now that it’s time to start writing out the addresses on the envelopes. I haven’t asked them for much regarding wedding planning so far (literally have only asked them to write out guests they would like to invite and provide us addresses so I can send STD’s and invites later on, nothing else I can think of) but they still haven’t done that for me. Has anyone else ever gone through this? What did you do to get the information you needed? I like staying organized but don’t want to be annoying by asking them. On the other hand if I’m not annoying, I know I will never get the addresses from them. Thanks!