I think The Final Frontier is suppose to take place just a few weeks or months after the end of The Voyage Home.
ST4 2286
ST5 2289
That's a looooong ass shakedown cruise. During which the bridge module at least has been completely replaced.
Memory Alpha gives it as 2287 after the cruise, could have sworn it was meant to be longer, what's up with the new bridge module then?
And a 6 year random gap to ST6.
Ugh, that fucking film...
The canon dating of
Star Trek V comes from a third-season TNG episode, "Evolution," where Data mentions that it has been 79 years since the last full-scale catastrophic systems failure aboard a Federation starship (back in 2287) -- Michael Piller later confirmed that this was indeed a reference to the fifth movie, which had just been released theatrically only a couple of months prior to the start of TNG's third season.
This dating is also used in the official Okuda chronology, which places
Star Trek VI in 2293 as a result, etc., which is also where the Memory Alpha-dating derives.
The bridge module was probably the first thing they replaced, only to find out they needed an even more different one to get the thing to work correctly, as they learned on the Nimbus III/center of the galaxy mission. I mean, why else would Kirk say, "I miss my old chair."?
Yup -- going strictly from one film to the next, it's clear that several major structural changes have occurred to the
Enterprise-A between movies; the bridge getting renovated being the biggest visual/temporal cue that some time has passed between the events of TVH and TFF.
Harve Bennett postulated something in the neighborhood of a six-month shakedown cruise (or thereabouts) -- however, with TSFS taking place in 2285, and TVH occurring only three months later (in early 2286), it's clear that a much longer timespan separates the two movies; likely between 9-12 months, at the absolute minimum.
As BillJ points out, a bunch of the first series of DC Comics stories set after
Star Trek IV took place during that interim period (2286-87), and there are several events there which could be viewed as possibly contributory to the
Enterprise-A's eventual widespread systems-breakdown as seen in
Star Trek V.