Could simplification be helpful? I'm thinking that in a conservative B2B industry, offering too much too quickly from an unknown probably gets your target's risk radar bleeping.
I spent a lot of time consulting for, managing projects in and selling into the wholesale banking industry - pretty conservative, slow to change and hard to break into. I found that simplifying both my offering and my message to focus on one or two major points of functionality and pain helped pique interest enough that I could get a decent conversation going, during which I could gently introduce other features and benefits.
In terms of long lead times I would suggest, if it's at all possible for your product or service, offering risk-free trials for a month or two. Manage the install, the maintenance, the training yourself, so the prospect has little or no reason to say no. Once they become users, and assuming your product or service is good, it will be easier to upgrade them to paying status.
A major feature of selling into the B2B space is to know who your buyer is. It is rarely an IT manager. It is rarely an HR manager. It is not always the Operations manager. It is very often, however, the Finance guy. This is not always true, of course, and many people have more or less influence over a given purchasing decision, but you need to know who those people are, what they care about and how to communicate with them in terms they each understand and care about.
To answer your question about how you decide whether to give up, I would advise you to do the above until you are 3-months from zero net worth. At that point, find a paying gig (consultancy, full-time job, whatever you need to do to keep your head above water), then use those three months to go all in on your startup - phone clients and push them hard, phone/email/meet with as many prospects as possible, and push, push, push. If it's going to fail, there is little harm in being harder-nosed / cheekier about the sales process. I would also, in that last 3-month period, look for a buyer for your technology, to at least get some return back on your investment. If, however, you land a contract or two during those three months, you can cancel the paying gig and continue with the startup.
Really good luck, whatever happens! Please do post an update - I think your story will be of interest to pretty much the whole of HN!
If it helps, I spend a reasonable amount of time helping people formulate business and marketing strategy. Happy to offer a specific opinion and ideas (gratis, of course) if you want to email me.