What are you doing when you are prescribed a 3hr 200xss ride but only have workouts that go to 2hrs/200xss?
I see the XSS is equal, so I guess I could just ride the 2hr workout and see how I feel and then do the extra hour in endurance and go over the XSS a little.
I have a 2hr endurance day recommended after this day.
Would what you do?
Use Magic Buckets and/or ride 3 hours.
Installed magic buckets today, thanks
You always have a choice in Xert. 
The advice is more descriptive than a strict prescription to follow. I realize many users treat it as an Rx, especially when accustomed to populated calendars with prescribed workouts, but that’s not how Xert works best. You control the dosages and when you take them (or not) during your “plan”.
There is a reason XFAI is called a forecast. It provides a framework to consider based on the settings you input and modify along the way. Day-to-day choices affect the forecast moving forward. Color too much outside the lines and the Adapt Forecast warning dot will appear.
With XATA’s blank calendar you have even more flexibility depending on your changing schedule and what you prefer to do within suggested guidelines. You control Focus and ramp rate plus Difficulty level through choices you make and how you ride a route outdoors. That in turn affects future days as calculated changes in form indicate.
The inherent flexibility in either program type takes getting used to, but one you’ve broken the must-do-this-today habit, you’ve cracked the code.
The Workouts Library is primarily comprised of workouts within the 45 minutes to 2-hour range. When available entries don’t match the upper-level goal for the day (XSS ratio/Focus and Difficulty), the closest matches are shown but you have options.
First recognize the target is approximate and not an exact number you must hit. In this case the goal is around 200 XSS in about 3 hours. On HIT days target Focus and Difficulty are most in play.
As @HAMILTON mentions XMB will guide you into closely matching the top-level specs while riding outdoors. XMB gamifies the process without selecting any workout. While you don’t really need to match each bucket number, most of us end up targeting those green checkmarks 
during a ride. If time allows, we’ll continue to accumulate more Low points.
Another option is to use Workout Designer to modify an existing workout on file to meet the specs. This isn’t hard to do using Copy, some Edit/Refresh experiments, then Save and name your copy. That custom workout will show up on recommended lists whenever suitable in the future.
An easer path to workout creation (for the day) is to run the XMB Workout Generator or Autogen to closely match the goal. If on a XATA program that option is available under [+] from the Planner.
The advantage to the XMB app on the road is that it dynamically adjusts intervals/recoveries as you fill the buckets. No need to send a workout to your head unit and try to replicate the steps outdoors. You can also manage the Difficulty level achieved by monitoring the Challenge Level gauge and Recovery timer. You can make things easier or harder if you want. 
XSS per hour establishes the Difficulty level achieved on any workout or ride.
Easy endurance and recovery pedaling is 50 XSS/hour or below.
Moderate rides are typically ~60 XSS/hour.
75-110 XSS/hour moves you into Difficult rating territory.
Point being there is a sizable strain difference between 200 XSS spread over three hours than two. 200/3 = 67 (2.5 diamonds) versus 200/2 = 100 (3.5 diamonds). You’re going to feel that difference.
3.5 may push your high/peak recovery further into the following day(s). If so, an Adapt Forecast warning will appear if you’re on an XFAI forecast. If you choose to adapt, the previous endurance day may change to rest/recovery recommended.
The warning dot appearance will depend on where you’re at TL-wise. For example, if you’ve been riding at 3.5 to 4 status stars for a while, a 3.5 Difficulty workout isn’t going to phase you much. If currently at 2 stars a 3.5 diamond workout will push you into red longer. Your recovery form will reflect red to yellow into the next day (or more) instead of a shorter recovery from red to blue had the strain been at 2 to 2.5 diamond level.
Sorry, I got a bit carried away explaining this one, but it helps to know your options and how a decision today affects the days ahead.
It’s a great platform, but it takes people like you to help me wrap my head around it. Thanks for the info. I’m going to give xmb a go and be more flexible in my thinking about the forecast going forward.
