I am working on a 16-plus-segment routing and was told that the ticket would need to be manually written by hand.

I expect to make significant date changes to the proposed ticket down the road. Is it going to be a nightmare to revalidate the ticket each time I make a change?

Thanks and happy holidays!

As others have stated many times, if the changes are just date/time, get the itinerary set, then have the ticket written with open dates. My last hand written ticket had a mix of specific flights/dates and open segments.

In principle, it doesn't matter whether the ticket is issued open-dated or with specific dates. Since it is not endorsed "VALID FLT/DATE SHOWN" then regardless of what the ticket says it is valid for any date on which you hold a reservation, and for any OneWorld airline which operates that route. So long as you have the reservations you don't need to do anything to the ticket - just turn up at checkin.

On Finnair in Helsinki, revalidation is SOP and you will have it done every time that you don't fly on the date on the ticket. Needless to say, there is no date on an open ticket so you will have to revalidate them. The process takes about 10 minutes depending on the number of people in line. Otherwise I have rarely had to revalidate any ticket, open or otherwise, that I have received. BA in London seems to occasionally want to but usually doesn't require it after thinking about it a little. But to answer your question, it involves a sticker being placed over the date with a new date on it and some other information. From my experiences, it usually takes a few minutes and is the equiv. of a sticker endorsement. It is done at the airport before flying so changing the dates involves just changing the reservation either with the issuing carrier or the travel carrier.

Happy holidays to you as well.

Agreed. Finnair seems to be at the outer reaches of OneWorld. HEL is the only place I have been which insisted on stickering an open-dated ticket. This only took a couple of minutes so no more than an irritation, but it's a shame that Finnair has to be different from the rest of the alliance.