The Art of a Great SE - How to Juggle!

As a Sales Engineer there is a tight balance between picking up new opportunities to support, keep up to date on your knowledge and skills, and focusing on closing the business you are currently engaged in.  If you neglect any of these it will impact on the bottom line, either sooner or later.

Let's look at each aspect and consider its importance.
A true sign that business is picking up is when you continually find new opportunities to work on.  It is important to continually offer support to these, or you lack business in your pipeline.  Depending on the speed of your sales cycle, you should bring these up to speed, and keep them warm, and keep a dialog going with these customers, as you work on their sequence of events to buy.  I find that inexperienced sales reps (and SEs!) will try to close these opportunities down before the customer is in any position to buy.  Every deal has its required steps to go through, and at the first stage you should work this out, and do everything in your power to shorten this.  Don't try to do things like POCs before they will have the required impact.  Its unlikely you'll change your customers timelines, so do your best discovery and plan out next steps.  Convert the deals you expect to be able to close into real opportunities and put less effort into the others.

Keeping up to date with your skills and knowledge is something you try to do in your spare time, as an SE, however you do need a certain amount of time to be sure of these abilities in front of customers.  If you find yourself lacking in that certain punch in front of your customers, then you need more preperation time to ensure you will be ready.  Take that extra hour to run through the presentation, demo systems, POC or whatever is necessary to be several steps ahead of everyone in the room.
If you feel like you are being asked to do impossible things, then you need to be the one setting expectations, and discussing agendas before the meetings.
The time spent preparing is critical so that you understand what you are showing, are prepared for problems, can lead the session in the right way.  If you need additional expert help, bring them in for the meeting with a defined role, and learn something new every chance you get.

Finally, closing the business you are engaged in is important for businesses of all sizes. If you are continually beginning opportunities without closing them, you will spend more and more of your time juggling expectations, meetings and time between different parties and won't get to the stage of concluding business and hitting your quota.  There comes a time in each opportunity where you could keep treading over the same ground and showing feature after feature, but if you don't draw a line and make a deal, then you won't get a return on the sales effort you have made.  If you have invested in a POC or major demo or whatever the technical side of a deal is, make sure you close down open questions, and progess the opporttunity into the decisive part and press on the sequence of events you agreed with your customer.  You did agree on a sequence of events before you put in the effort didn't you!?
This is something that grows with experience, but don't spend the bulk of your time on customers until you are sure that they aren't just learning, or checking on the market or other tyre-kicking kinds of activities.  Convert the deals you feel most confident on to this category and watch the need grow slowly in the others.
Learning to balance these three areas will reward SEs and sales teams and get the best out of your most valuable resource - time!

If you have trouble working out how much of your time you should spend in each area, review your calendar with your manager.  You should be able to work out better ways to spend your time, and push out meetings that aren't maximizing the use of your time.