How do I know if my employees are committed to the company long-term?

If you want employees to commit to your company long term the company needs to commit to the employees long term. When a high performer is plagued with uncertainty their commitment can vanish quickly. It takes a long time to build trust but only an instant to lose it

Check if they are consistently engaged and interested

If they show great enthusiasm for the company as opposed to the job itself. One sign is if they have applied for multiple positions at your company over the years. Are they familiar with your company's work/products? Do they know a bit about the company's history? Do they exhibit passion?

You can never be to sure. Yet, the ones that give you the most effort. Always on time and gets the job done are the ones that will stand an stick it out

I think it depend on personal interests

Their behavior reflects their commitment level

Ask the employee if they are happy in his or her work. Do you have any suggestions to make it more productive?

Willingness to stay even if other higher paying opportunities arise.

You never will know unless you create a space where they feel comfortable discussing their goals and next steps. And then, ask them. But the precondition is not optional.

What kinds of things they keep on their desk. How often they see the people they work with out of work.

In my company, the only real 'long-term' employees are usually those in management. Far as committed to the company goes, management is mostly there just for the money or benefits.

Ask them upon hiring and throughout yearly self assessments

When interviewing I would ask about plans to grow in the company. If they come up with an automatic response, I’ve thought about staying with the company. Even a slight pause is OK. But if they have to really think about it, then odds are they haven’t made the mental commitment to stay.

I am in the BPO industry for 6 years now and from what I have observed, employees that stay are the ones who are happy with the office environment, has a transparent and friendly relationship with bosses and coworkers, happy with the pay and benefits, and happy with his/her well-being.

An open line of communication, open goal list, and reaching those goals with the employee, for and by the employee.

Seeing how they feel about work, how they perform, and their overall Morale

you can tell who is in for the long haul after the 1st month

If there is scope for career growth. At the moment I don't see any.

YOU NEVER DO - so foster an atmosphere to keep them encouraged and engaged. Make it clear you are all in it for the long haul, and want them to know that too.