What do you think about collecting consecutive banknotes?

Hi. Sometimes I find consecutive banknotes ads. Is it usual to collect consecutive banknotes or not?

http://www.ebay.com/itm/B-V-B-2x-Consecutive-Pick-75b-Madagascar-1994-500-Francs-aUNC-/302457792997?hash=item466be3a9e5:g:qHMAAOSwoF1ZwB1e

http://www.ebay.com/itm/B-V-B-2x-Consecutive-Pick-76-Madagascar-1994-1000-Francs-aUNC-/302457806198?hash=item466be3dd76:g:cGoAAOSwErFZwCBJ

http://www.ebay.com/itm/MOLDOVA-banknotes-1-leu-X-2-pcs-2015-new-type-UNC-Excellent-consecutive-numbers-/122691351727?hash=item1c90f974af:g:LSsAAOSwImRYVsGa

http://www.ebay.com/itm/Portugal-50-Escudos-28-02-1964-UNC-2-PCS-Consecutive-Numbers-/182776861359?hash=item2a8e5992af:g:7HsAAOSwX0NZwWRZ


And then. Can you make an estimation for this lot of banknotes from French Revolution? Many thanks.

http://www.ebay.com/itm/B-V-B-Lot-of-5-France-assignats-Original-Watermarks-French-Revolution-notes-/302392903611?hash=item46680587bb:g:ZJ0AAOSwDvFZddSv

Many collectors of world banknotes try to have at least two of a note. This facilitates exhibiting, and allows notes to be appreciated with the back and the face being able to be seen at the same time. But just as many folks collect single notes, so that they can have a wider variety of notes in their collection. Really it is how you like it to be. I have doubles of most of my notes.