I keep absolutely everything - and recommend to anyone who listens to do so as well. I do run my own company, so legally I need to keep all receipts and statements for 5 years - it also helps that I'm anally retentive in my processes and checking everything. Thankfully this attitude has rubbed off onto my husband and other family members which has served us well, when things have gone awry.
I keep all receipts very carefully but have had to badger and nag my husband to keep his. Now, he empties out a great wadge of them out of his wallet once in a blue moon and I have to try to make sense of them.... but that's still better than him not keeping them at all!