How do current spikes over limit affect Lithium battery life?
So according to the discharge characteristics you posted, the capacity actually goes up at higher currents, which is unusual. Granted the potential is a little lower so the total energy (Wh) might be roughly the same. In order to know how much discharge time you're losing because of the spikes, you'd need to know how wide they are. If you integrate the sample you collected and divide it by how long that sample is, you get a correction factor. Then take your 4000 hours and divide it by this factor to get the expected discharge time from the observed current profile. If the result is significantly different than what you actually get, then there's something else going on: either your profile is inaccurate or you're pulling more current than you think you are.