I actually think its super interesting that you asked this because i hadnt even thought about these things.... Or i mean, the future of my blog i have thought about. But not so much about telling others.
My family know i blog, but my friends dont and i want to keep it that way. If i were to date someone for a few months i am pretty sure that they would realise that i spend quite alot of time online and writing, but also i would need my own silent time to sit and blog. So they would suspect something, and if they were to ever use my computer they would see the bookmark as well as in the history my blog .As well as on my phone i have the blogger app, so i mean im not super descrete about it if i put it that way. But i wouldnt mention it, i wouldnt bring it up or let them read it. Infact if my boyfriend were to find out about my blog i would most probably make him swear to not read it.... it feels like its a very personal thing, even if i am not super personal on it anymore. But reading into my past posts, if its someone i know its like they would be picking inside my brain or reading my diary. When its online readers and people i dont know who read my blog or older posts, its like im not really aware of it. If i were to see thousands of people all standing infront of me when i blog then i am pretty sure my heart would start slamming fast and i wouldnt be able to type a single word. But when its just a number, when i just see xxxx views then i dont think so much about it, it doesnt feel like its actual people, hahaha.
But to answer the question, its hard to know... of course if i am still blogging and im engaged or something then well, i am sure everything about my past would already have been spoken about so that i dont think it would matter so much to me. But if its just a boyfriend when im X years old, its not really the same thing unless i have been with him for like 3 or more years. Then its more serious (yes.... 3 years to make it serious, lol... no.) and i would have more trust and feel safe enough to show this side of me.
Because in actuality, the blog girl and the real me... sometimes feel different. In the sense that i am quite open on my blog compared to in real life. I have a hard shell around me, which only now i am realising as i am in the world of dating and realising just how scared i am to let someone in. My blog is a security and comfort for me (hence why a few weeks ago when i was getting lots of negative comments it really did affect me at first because suddenly my safe place was no longer a safe place.).
Do i feel that people judge me when i tell them that i blog? Well i agree with you on the description, blogging has always seemed like a silly thing and i would feel super weird telling my friends i blog. But also because of the topic of my blog. I have had people i know tell me they found my blog and they think its great and dont judge me at all, but i dont think i would be the one to tell people..... thats not really how i am, but also if i tell people i blog they would want to read it, and im not comfortable with that :)
And finally.... how long will i blog? Until i no longer want to. Whether its because i get loads of hate and negativity, i dont have time, no longer have anything to write about or because i get hacked or something else.... who knows. But i dont have any certain date or time when im going to stop blogging. Will i be 50 years and blogging? Who knows... i might be an agony aunt or advice collumnist in a magazine instead, or might have my own proffessional website. But for now, i am still young. I have been blogging for 5 years officially, though i start in 2009 (so 6 years really). So really, making money from my blog would be a good idea.... but like i said, i am still young and i see blogging as more of a hobby or a volunteer job rather than something i will spend my life doing. I would of course like to grow it, start earning money from my writing but how to go from step A to B... thats the hard part. (If you have advice about this, you can please email or comment me:))
Long answer... but i guess i had alot of thoughts about these questions!!!