ISBN's, How Many Does One Ebook Need?

My book is going into final editing, I have a possible ebook cover for Walk Forward, what do I need next?

Time to think about ISBN's for each version of my book. Since I want my book to be available in various formats, I will most probably buy the set of 10 ISBN's. I know that I will have a .pdf, ePub and maybe a few hard copies of the book down the road. I want to be able to track the book myself. I know that many books have similar titles but each has a unique ISBN.

I plan on uploading the book to Amazon, Smashwords and any vendor that will take my ebook. Down the road, I might want a hard copy too. I know that the ebook cover I made will have to be revised for a hard copy book where the cover wraps around the book. I have no idea now as to how many pages a  hard copy of my book might have. In hard copy, my text might appear in larger font for my target of young adults, but then again, the book is also for adult readers.

I want to submit my book to any online publisher willing to let me upload it, thus, expect more than two book formats. Perhaps, I will publish a version with photographs and one without, this would require another ISBN! Maybe my book will have a new cover or need revisions sooner than I might expect.
Guess it is better to buy the batch of 10 than run out!

The ISBN is the unique identifier for a particular format of the book. I don't think I really need 10 ISBN's but since 10 cost the same as 2, and I am sure I need at least 3, I might as well buy the set of 10.

Are there any negatives to buying 10 ISBN's and not using them all immediately? I don't know but plan to call Bowker, the only company allowed to sell ISBN's. I wonder if there is a penalty in not assigning all 10 ISBN's in a reasonable time period? I can not imagine that it will take me 10 years to write a second book although I have been writing content for my first book for more than 20 years!

Is there a fee or penalty for holding my 10 ISBN's, which I assume will be numbers in a series? I don't know for sure, heard there was some sort of  annual fee? I must find out as hate to commit to annual fees.

What about translations? I assume if someone creates a translation of the book, the new translated version will need another ISBN. If I change the cover design and a few photographs, this would require ISBN's!

Maybe my first ebook will need more revisions than I can now possibly imagine?

Ten ISBN's seems much for my first attempt at an ebook and my second book is but a vision. I have read Bowker's section on why one should buy an ISBN.

No matter the price or how many, as a librarian, I know that an ISBN is priceless!