Irene
My db has pretty close to 28,000 customers in the db.  My combo boxes run just fine.  You just type in the start of the name and it "jumps" to what is being typed. You may need additional fields in the combo box to differentiate between Smith, Jim for instance however.

A better way is to take a look at the continuous forms and searches that Richard has demonstrated in some of his videos.  Take a look at Search Form 2.0 for a better way of bringing up your customers.

Hi Scott.  
Thank you for your response.  
I think I have to join the TechHelp membership to watch more of Richard's videos.

Irene you can still watch the free videos.  That being said, I really feel that the TechHelp membership is some of the most wise money I've ever spent.  Well worth giving up a coffee or two every month. I like the gold because I can download the sample databases and the access to  the code vault.

If there's any way to group those customers, you might also benefit from Cascading Combo Boxes.

Hello Irene.  I just thought I would put my 2 cents worth in, in case you were still debating on what to do.

I have had an account now for almost 10 years.  After finding Richards site, I wrote myself a few databases using what I had learned at that time.  Between all of the changes in technology, especially since COVID, and how things have changed in my personal and work life, I am in the process of upgrading my databases to accommodate the changes and so I can do more with them.

Until recently I haven't been active on the site, but during that time, Richard has made AWESOME changes to the site and how it works.  When I checked out his site again I instantly upgraded to Tech Help SILVER.  Within 1.5 days, I upgraded to Tech Help GOLD.  Scott is right.  BEST money ever spent.  BEST choice I ever made, and BEST money ever spent.  The benefits from Silver to Gold are way more beneficial for learning!  :)

Thanks Ramona. You should put that on the Testimonials page. 😊😁

Never thought of that.  Ok.  Done.  I added a bit more too.

Thank you Ramona for your thoughts.  I'll keep that in mind.  I just joined Silver 2 days ago and already getting benefits from it.  I'm so grateful for finding Richard's site while browsing youtube.  My employer is trusting me to create a database and I didn't know the possibility of me creating it until I found this site.  Thank you all.

I have created a database that does not have as many records, but once it starts getting bigger than Ben Herr in a drop down list, I have a works around that I use the Customer ID or the ID number that is unique so it looks that up first. That way if you start typing in the unique ID number it will jump to it in your drop down menu.
This has saved me many times and yes I design my forms on others using it, so trying to think ahead as to what issues bugs me will be harder for them.
I used to use an old computer called "Burroughs" and a customer search was based on knowing their Customer Number, now creating my own I now know how well that works.
I also in my forms leave an option to look for Customer by Name to see the possible  Customer ID Numbers to type in.

There's also Search As You Type which filters the box as you type characters, but that involves some coding. I cover it in Access Developer 8 and the Search Seminar.