Memory formation and memory retrieval are very different tasks, so one should be specific when making claims like "Caffeine helps long term memory." For example, if caffeine only hinders long term memory formation, but not retrieval, then this would suggest using it during an exam, but not while studying. If vice versa, then vice versa.

Unfortunately for our purposes, the authors of your first article have blurred this distinction in their abstract, no doubt because it was not the subject of their study: their method was to add caffeine to rats' water supplies, without controlling the timing of the doses in relation to the events of formation and retrieval.

I was happy to find your last article addresses precisely this question:

Groups of 12 adult male Wistar rats receiving caffeine (0.3-30 mg/kg, ip, in 0.1 ml/100 g body weight) administered 30 min before training, immediately after training, or 30 min before the test session were tested ... Post-training administration of caffeine improved memory retention at the doses of 0.3-10 mg/kg ... but not at the dose of 30 mg/kg. Pre-test caffeine administration also caused a small increase in memory retrieval .... In contrast, pre-training caffeine administration did not alter the performance of the animals either in the training or in the test session. These data provide evidence that caffeine improves memory retention but not memory acquisition, explaining some discrepancies among reports in the literature.

Nice article, IMO. Its conclusion might suggest drinking caffeine right after study sessions (or in breaks between them, while ruminating on the ideas) is the best strategy. On the other hand, perhaps in the long term, the non-specific effects of the first study would dominate.

Personally, I'm definitely unconvinced by these data as to how I should be using caffeine, but as you can see you've got me very curious!