Hey there @Claudia01041 -- great questions! 

Right now there is no way to allow invitees to choose the duration of a booking. This is because the duration is “locked in” within the event type’s setting, just like with other settings such as: 

• start time increments
• availability
• notifications
• event name
• ...and all other settings within the event type setting editor!

This also means that the workaround you have already discovered (setting up a separate event type for each duration) is the best workaround there is, to date. That said, there are some ways to make the invitee booking experience more seamless that you might be interested in!  Let’s go over those. 

Routing Forms

Using Calendly Routing Forms, you can set it up so that invitees answer a question or two and are then automatically routed to the correct event type (hereafter referred to as “ET”). Routing forms let you request information such as industry, company size, specific interests, etc. from website visitors and automatically direct them to a specific scheduling or web page based on their responses. It's great for screening and qualifying sales leads on a website or matching clients or students to the booking page of the right subject-matter expert based on their interests, program, or other criteria. You can read more about setting up routing forms, here!

 You could set this up in a manner such as:

• you create a core ET with a single duration, then “clone” that ET as many times as you need to, only updating the duration of the clones + the name (ex: “ET Name: 30 Minutes” + “ET Name: 45 Minutes” + “ET Name: 60 Minutes” etc.)
• you make all of your conference room ETs “secret” so that they are not visible on your public booking page
• you set up an ET for each duration that you need to offer
• you create a routing form that asks a question such as, “How much time do you need to reserve a conference room for?” or, “What duration of time do you need to book the conference room for?”
• you set up routing logic that auto-directs the invitee to the appropriate ET once they select from the durations offered
• the invitee books their ET 
• you get notified of the booking 

Your invitee routing experience would then look like: 

• you share the link to your routing form and/or embed the form on your website 
• the invitee answers a question such as, “How much time do you need to reserve a conference room for?” or, “What duration of time do you need to book the conference room for?” 
• the invitee selects the duration from the options you provide as answers on the routing form
• the invitee is auto-routed to the ET that has that duration set up 
• the invitee books their ET without ever knowing that there were others to “choose” from
   

 Important Note: in order for your conference rooms to be booked simultaneously, you will have to set them each up under an additional host (a different email address) within a Team Page. You will not be able to have multiple ETs booked in an overlapping way under your solo-user account. I am telling you this in case you hadn’t discovered it, yet. Once you have a Team Page set up, you can use a Collective Event Type (on the Standard plan) or a Round Robin Event Type (on the Standard or Teams plan) as a one-on-one event type for each conference room on the Team Page (read more here about using these ETs as one-on-one events on Team Pages). 

You’d need to be on our Standard or Teams Plan to set up a Team Page, add additional users (one user/host for each event type/conference room) and then set them all up to take place at the same time. You can read more about our plans, pricing and features on our Pricing Page! Note: an annual subscription will result in a 20% discount for all paid plans!

I hope this helps! 

p.s. check out our Getting Started Guide for more tips + tricks as you learn the Calendly ropes!