There was once a huge controversy over what exactly constitutes a journey logbook. Everybody agreed you had to have one, but what is it? The original requirement was set out in 1944 without a precise definition. ICAO Annex 6 changed all that a few years ago, but we are still left with a decision on where the book should be kept.
The only document we have that comes even close to satisfying all the requirements are the Flight and Maintenance Log that we complete for every flight. You will have to examine your version to see if it also satisfies the ICAO.
As for how long you need to keep it on the aircraft, that's where it gets tricky. More on that below.
What follows are quotes from the references listed below, with comments shown in blue.
[1944 ICAO Chicago Convention, Article 34] There shall be maintained in respect of every aircraft engaged in international navigation a journey log book in which shall be entered particulars of the aircraft, its crew and of each journey, in such form as may be prescribed from time to time pursuant to this Convention.
11.4.1. The aeroplane journey log book should contain the following items and the corresponding roman numerals:
11.4.2 Recommendation.— Entries in the journey log book should be made currently and in ink or indelible pencil.
11.4.3 Recommendation.— Completed journey log book should be retained to provide a continuous record of the last six months’ operations.
Paragraph 11.4.3 recommends the journey log book be "retained" but doesn't say it has to be on the aircraft. I think if you have electronic access to them you should be okay.
[EASA Acceptable Means of Compliance (AMC) to Annex III - Part-ORO] §AMC1 ORO.MLR.110]
2.8.2 A journey log book shall be maintained for every aeroplane engaged in international air navigation in which shall be entered particulars of the aeroplane, its crew and each journey.
220.127.116.11. Recommendation.—The aeroplane journey log should contain the following items:
[European Union Regulation No 965/2012, §ORO.MLR.110] Particulars of the aircraft, its crew and each journey shall be retained for each flight, or series of flights, in the form of a journey log, or equivalent.
[AC 91-70A, ¶2-3.p.] Article 34 of the Chicago Convention determined that it was extremely important that each aircraft have a journey logbook. Annex 2 requires this standard for operations engaged in international aviation. The aircraft should carry a journey logbook containing the particulars of the aircraft, crew, reporting points, communication problems, and any unusual circumstances surrounding the flight. Note: An electronic version of the journey logbook is acceptable but you should retain the data at least 90 days for support in the event of an oceanic error.
We scan every flight log and have it electronically available at our home base on a full time, secured, network drive. We can download any log from anywhere with an Internet connection. We only carry enough past flight logs on the aircraft to prove a maintenance airworthiness release, a valid VOR check, and an RVSM check. Will this pass muster? I think so. I have been SAFA ramp checked and the subject never came up.
Portions of this page can be found in the book International Flight Operations, Part VIII, Chapter 25.
Advisory Circular 91-70A, Oceanic and International Operations, 8/12/10, U.S. Department of Transportation
European Union Regulation No 965/2012, Technical requirements and administrative procedures related to air operations, 5 October 2012
ICAO Annex 6 - Operation of Aircraft - Part 1 Commercial Aircraft, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part I, July 2010
ICAO Annex 6 - Operation of Aircraft - Part 2 General Aviation, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part II, July 2008