Employees at big tech companies tend to frequently switch jobs, a recent Business Insider article noted.

People working for Uber stick around just over a year. Employees at Airbnb, Twitter, Snap, and Apple stay almost two years on average.

To me, these results reconfirm that job hopping in tech is a thing. In some ways, it’s a bit of a relief to know that I’m not the only CEO struggling with the hyper-liquidity of the Silicon Valley job market — and the enormous cost of short-tenure employees to a growing business. It’s a huge challenge for many of us, but it’s also problematic for employees.

To be clear, job hopping is a losing game. Not just for me and other business owners out there, but also for the people doing the hopping.

It may be a short-term tactic that gets you someplace new but as a long-term strategy the cons outweigh the pros — and there are a few good reasons why.

Relationships are currency

They’re how we get jobs, connect with new and valuable contacts, make inroads in areas of professional importance to us. But the most valuable relationships—the ones that are deeply useful, enriching and enjoyable—start with trust, usually the kind that takes time. It’s the people who have shared professional foxholes with you, worked side by side on the toughest projects, and observed your performance, grace under pressure, humor and integrity firsthand. You will get your best recommendations, your most amazing leads, and the most useful advice from these people. They will go to the mattresses for you.

And although it’s true that as a short-timer, you may still leave a positive impression behind, you won’t take these kinds of relationships with you when you go – simply because they require an investment of time that you haven’t given.

You miss out on valuable learning

If you’re at a company for two years or less, you’re cheating yourself out of real learning opportunities that almost inevitably would make you smarter, better, and — yes — more attractive for great roles down the line. When you first start a new role, so much of those initial months is really just figuring things out— the culture, your job, what you don’t know, who you should know, etc. If you leave after a few months, you haven’t given yourself a chance to grow into the job or as a professional. You haven’t opened yourself up to the lessons the role could teach you.

A transactional attitude doesn’t inspire employers

If you have one — maybe, maybe two — short stints on your resume, no big deal. We all have those and there are usually good reasons why: a partner gets a better job so you move out of state, you see clearly it’s not a good fit so you choose to fail fast, you get recruited for a job that’s too good to pass up, you have a life circumstance like an ill parent to focus on. Totally fine. But if you’re serially moving on after one or two years, you look like you have zero loyalty. Like you can’t be bothered to commit. Like it’s a one-way street where employers need to wow you — not a two-lane road of mutual giving and support.

It’s difficult for companies — that spend a lot of money on onboarding and offboarding employees — to feel relaxed about hiring someone who seems to regard jobs only as transactions. You seem like a greater risk to take than someone who has passion for what they do and the desire to stick around and see it through. And these risks are substantial and potentially material: in time, loss of productivity, the funds required to recruit, interview, hire and onboard someone new, etc.

We’re in a job market right now that’s hot for the best talent – and it’s understandable that people feel empowered to take on new and exciting roles. In many cases, that may be the wise thing to do. In general, though, it’s wise to take jobs where you can reasonably plan on sticking around for a minimum of three years. The rewards of doing so are not to be dismissed — and merit real consideration.

Read next: The 10 best games of 2017