I'm pretty new to this so I only have one pair of domains. ****Token com and ****Tokens com. The former could be the name of a startup, while the latter... not really. So I guess the singular is more valuable. If I receive offers for it, I'll try to throw in the plural as a bonus in order to get a good price. I just have to wait and see if it works. As @Reddstagg mentioned above, BOGO deals are usually well received by customers. And yet judging by the experiences that @NamesBond shared here, this may not be the case when it comes to domains. I do think that owning lots of pairs can become cumbersome when you have a huge portfolio.