From the defeat of Prussia in 1806 (the actual start of the shift varied from 1807 through 1809), the source of oak timber and plank (from 1807) as well as masts (from 1808) and pine timber (from 1809) shifted to British North America from Europe (all countires). The source shifted back in 1814 along with the plunging need for all forms of such woods.
See Albion, Robert Greenhalgh. Forest and Sea Pwer: The Timber Problem of the Royal Navy, 1652-1862. 2000 Reprint of the the 1926 original.
Allowing Napoleon take Danzig in 1807 (the Royal Navy sending only four sloops of war to aid the Prussian garrison and the land forces were tardy in getting into the Baltic at all), makes one wonder at English strategic wisdom.
Then, if the French fleet was so poor, from where comes the need to build up the fleet numbers and not allow this manpower to serve in the land forces to overthrough Napoleon?
The answer lies in the use of the Royal Navy to get it "head start" in other parts of the world and, yes, gathering gold which could be used to finance their "allies" on the continent.
I was not following the ship-life comment and do not know the source of the 10 year comment (the Royal Navy went from 11.75 years before the wars to 8 years after the outbreak of the revolution; see below after I make some comments of Roger's The Command of the Ocean).
Roger's work (before you ask, I have read both The Safeguard of the Sea and The Command of the Ocean) is rather weak on the technology of ships, woods and duration. To venture an opinion, Roger's works are very detailed (which is good), although the writing is from a "point of view" (depending on the reader's desire this may be good, bad, or indifferent) and have a tendency to be dismissive when difficult topics arise (which is bad - take, for example, his "Science versus Technology" chapter where he dismisses any claim of superior French ships by saying they were captured or sunk more frequently - this without any attempt to eliminate other causes for such losses - weather, bad sailing, poor fighting, bad command or other such combinations).
Ship life (duration) depended upon the type and quality of wood as well as construction.
Duration and endurance are not the same due as treatment, decay and use (wear and tear), yet endurance data gives a starting point for interpolating duration. I shall return to duration but first, endurance.
The average endurance of common English oak was 25 years. One source on the dndurance of oak shows:
American oak - 10 years
Russian casan oak - 10 years
French oak - 15 years
Polish oak - 15 years
German oak - 15 years
Danish best oak - 20 years
Swedish best oak - 20 years
English common oak - 25 years
English best oak - 40 or 50 years
http://books.google.com/books?id=HkgNAAAAIAAJ&pg=PA248
This is rather more "neutral" as it is before considering wear and tear matters. Albion notes that the average duration was between 10 and 20 years. (He notes average duration was 15 years over two centuries.)
So, as for the Royal Navy, according to the Report of the Commissioners of Woods, Forests & c published in 1792 the average duration of their ships from 1760 to 1788 was 11.75 years. After the start of the French Revolution it fell to something like 8 years arising from wear and tear (8 years being mentioned by many sources, including Albion who goes into the Royal Navy's problem with dry rot - one ship, Queen Charlotte, was completely rotten two years after lauching and before she went to sea). After the wasrs, in the 1830's, the average duration for the Royal Navy was estimated at 13 years.
For a discussion on changes in average duration see:
http://books.google.com/books?id=fMQPAAAAQAAJ&pg=PA659
Note the difference in the "starting point" of French (15 years) and English (25 years).
The effect of using wood of these different sources was realized, generally. See the interesting table (not warships, although as part of a discussion of warships) where "Ships built of Colonial Timber" had an average duration of 3 years 6 months and "Ships built of Baltic timber" had an average duration of 8 years 3 months.
http://books.google.com/books?id=dQUbAAAAYAAJ&pg=PA130
I realize the aspect of fir versus oak is not address in this post. Different woods are important (as the Russian fleets - Batlic versus Black Sea fleets show dramatically - Storch's volume 7 of his Russland under Alexander dem Ersten shows this as each ship of the line's condition is explained not visable on the Google work as the major ships were on fold-out pages, so one needs an original).
For now. - R